iDEAL gAS lAW

Ideal Gas Law

• An Ideal Gas (perfect gas)is one which obeys Boyle's Law and Charles' Law exactly.
• An Ideal Gas obeys the Ideal Gas Law (General gas equation):

PV = nRT

where
    P=pressure
    V=volume
    n=moles of gas
    T=temperature
    R = gas constant (dependent on the units of pressure, temperature and volume)
        R = 8.314 J K^-1 mol^-1 if
            Pressure is in kilopascals(kPa)
            Volume is in litres(L)
            Temperature is in kelvin(K)
        R = 0.0821 L atm K^-1 mol^-1 if
            Pressure is in atmospheres(atm)
            Volume is in litres(L)
            Temperature is in kelvin(K)

• An Ideal Gas is modelled on the Kinetic Theory of Gases which has 4 basic postulates:

1. Gases consist of small particles (molecules) which are in continuous random motion
2. The volume of the molecules present is negligible compared to the total volume occupied by the gas
3. Intermolecular forces are negligible
4. Pressure is due to the gas molecules colliding with the walls of the container

• Real Gases deviate from Ideal Gas Behaviour because:

1. at low temperatures the gas molecules have less kinetic energy (move around less) so they do attract each other
2. at high pressures the gas molecules are forced closer together so that the volume of the gas molecules becomes significant compared to the volume the gas occupies

• Under ordinary conditions, deviations from Ideal Gas behaviour are so slight that they can be neglected
• A gas which deviates from Ideal Gas behaviour is called a non-ideal gas.

Ideal Gas Law Calculations

Calculating Volume of Ideal Gas: V = (nRT) ÷ P

What volume is needed to store 0.050 moles of helium gas at 202.6kPa and 400K?

PV = nRT

P = 202.6 kPa
n = 0.050 mol
T = 400K
V = ? L
R = 8.314 J K^-1 mol^-1

202.6V = 0.050 x 8.314 x 400
202.6 V = 166.28
V = 166.28 ÷ 202.6
V = 0.821 L (821mL)

Calculating Pressure of Ideal Gas: P = (nRT) ÷ V

What pressure will be exerted by 20.16g hydrogen gas in a 7.5L cylinder at 20^oC?

PV = nRT

P = ? kPa
V = 7.5L
n = mass ÷ MM
  mass = 20.16g
  MM(H₂) = 2 x 1.008 = 2.016g/mol
n = 20.16 ÷ 2.016 = 10mol
T = 20^o = 20 + 273 = 293K
R = 8.314 J K^-1 mol^-1

P x 7.5 = 10 x 8.314 x 293
P x 7.5 = 24360.02
P = 24360.02 ÷ 7.5 = 3248kPa

Calculating moles of gas: n = (PV) ÷ (RT)

A 50L cylinder is filled with argon gas to a pressure of 10130.0kPa at 30^oC. How many moles of argon gas are in the cylinder?

PV = nRT

P = 10130.0kPa
V = 50L
n = ? mol
R = 8.314 J K^-1 mol^-1
T = 30^oC = 30 + 273 = 303K

10130.0 x 50 = n x 8.314 x 303
506500 = n x 2519.142
n = 506500 ÷ 2519.142 = 201.1mol

Calculating gas temperature: T = (PV) ÷ (nR)

To what temperature does a 250mL cylinder containing 0.40g helium gas need to be cooled in order for the pressure to be 253.25kPa?

PV = nRT

P = 253.25kPa
V = 250mL = 250 ÷ 1000 = 0.250L
n = mass ÷ MM
  mass = 0.40g
  MM(He) = 4.003g/mol
n = 0.40 ÷ 4.003 = 0.10mol
R = 8.314 J K mol^-1
T = ? K

253.25 x 0.250 = 0.10 x 8.314 x T
63.3125 = 0.8314 x T
T = 63.3125 ÷ 0.8314 = 76.15K

Charles' Law:

Assuming that pressure remains constant, the volume and absolute temperature of a certain quantity of a gas are directly proportional.

Mathematically, this can be represented as:

Temperature = Constant x Volume
or
Volume = Constant x Temperature
or
Volume/Temperature = Constant

Substituting in variables, the formula is:

V/T=K

Because the formula is equal to a constant, it is possible to solve for a change in volume or temperature using a proportion:

V/T = V₁/T₁

Explanation and Discussion:

Charles' Law describes the direct relationship of temperature and volume of a gas. Assuming that pressure does not change, a doubling in absolute temperature of a gas causes a doubling of the volume of that gas. A drop of absolute temperature sees a proportional drop in volume. The volume of a gas increases by 1/273 of its volume at 0°C for every degree Celsius that the temperature rises.

To explain why this happens, let's explore temperature and volume in terms of gases. Temperature is an average of molecular motion. This means that, while all of the gas molecules are moving around their container in different directions at different speeds, they will have an average amount of energy that is the temperature of the gas. The volume of the gas is the size of its container because the molecules will move in a straight line until they impact something (another molecule or the container). However, to move as they do, the molecules require kinetic energy, which is measured by temperature.

So, the volume and temperature are very closely related. If the temperature was not sufficient, the molecules would not be able to overcome the weak forces of attraction among them and would not be able to fill the container.

Charles' Law must be used with the Kelvin temperature scale. This scale is an absolute temperature scale. At 0 K, there is no kinetic energy (Absolute Zero). According to Charles' Law, there would also be no volume at that temperature. This condition cannot be fulfilled because all known gases will liquify or solidify before reaching 0 K. The Kelvin temperature scale is Celcius minus 273.15 °. Therefore, zero Kelvin would be -273.15 ° and any Celcius temperature can be converted by to Kelvin by adding 273.15 (273 is often used).

Any unit of volume will work with Charles' Law, but the most common are liters (dm³) and milliliters (cm³).

Calculations with Charles' Law

Let's try a problem with Charles' Law. For example, let's try to solve for an unknown volume of a gas. The unknown volume is at 32°C. At 18°C the gas occupied a volume of 152 mL.

Set-up

First, we must convert degrees Celcius to Kelvins. To do this, we add 273 to the Celcius measure. So:

32°C + 273 = 305 K
18°C + 273 = 291 K

Estimate answer

We know that the temperature and volume are directly related. The temperature only went up a little bit (slightly more than 5%). So, we can expect the volume to increase by about 5%, which would be about 7.5 mL. Now, we can use the formula. (Really, we should use fraction ratios.)

Plug values into formula

Our formula is: V/T = V₁/T₁

In this problem, V = 152 mL, T = 291 K, and T₁ = 305 K. V₁ is unknown. Therefore, we can arrange the formula as:

152 mL/291 K = ? /305 L

Because this is a direct proportion, we can multiple the means and extremes to create an ease to solve equation:

152 mL x 305 K = 291 K x ?

Which can be divided by 291 K to yield:

152 mL x 305 K / 291 K = Volume₁ = 159.3127 mL

However, we only have three degrees of precision in this problem, so our answer is: Volume₁ = 159 mL.

Check

To check our answer, we need to compare it to our earlier estimate. We expected the volume to increase by about 7.5 mL, and it increased by 7 mL (7.3 before round). This answer is acceptable.

Continued Study
For continued study, you can visit our Charles' Law bonus page. You can also test yourself. You can also learn about Jacques Charles.

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Sources:

Brown, Theodore L., H. Eugene LeMay, Jr. and Bruce E. Burston, Chemistry: The Central Science, Englewood Cliffs, NJ: Prentice Hall, Inc., 1994

Dorin, Henry, Peter E. Demmin, and Dorothy L. Gabel. Prentice Hall Chemistry: The Study of Matter, Needham, Massachusetts and Englewood Cliffs, New Jersey: Prentice Hall, Inc., 1989.

Roper, Gerald C., "gas laws" Groliers New Multimedia Encyclopedia, Release 6, 1993

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Team # 12596

[ Main ] - [ Sections ]

Choose the best answer.

Top of Form

Question 1: 5.0g of an ideal gas occupies 9.2 L at STP. What volume would it occupy at 120°C?

13 L

3 L

130 L

None of These

Question 2: 5.0g of an ideal gas occupies 9.2 L at STP. What volume would it occupy at 0°C and 93 mm Hg?

7.5 L

10 L

75 L

None of These

Question 3: 5.0g of an ideal gas occupies 9.2 L at STP. What is the molecular mass of the substance?

12 g

13 g

78 g

None of These

Question 4: 5.0g of an ideal gas occupies 9.2 L at STP. What volume would it occupy at 120°C and 92 mm Hg?

19 L

109 L

0.42 L

None of These

Question 5: Calculate the volume occupied by 12.0 g of CO₂ gas at 245 mm Hg and -35 °C.

5 L

10 L

15 L

None of These

Question 6: A sample of an ideal gas occupies 1.4 L at 28 cm Hg and 52 degrees C. Calculate the number of moles in the solution.

19 mol

0.019 mol

1.9 mol

None of these

Question 7: An Ideal gas has a volume of 15.0 L at 15°C and 735 mm Hg pressure. At what temperature would it occupy a volume of 30.0 L at 785 mm Hg?

615 K

512 K

128 K

None of these

Question 8: A sample of ideal gas occupies a volume of 238 mL at STP. To what temperature must the sample be heated if it is to occupy a volume of 185 mL at 2.25 atm?

94.3 K

477 K

477°C

None of these

Question 9: Increasing the pressure on a sample of gas increases its temperature, but its volume remains the same. What law best explains this?

Avogadro's Law

Graham's Law

Ideal Gas Law

Avogadro's Interpretation of Guy-Lassac's observations

Question 10: A few minutes after opening a bottle of perfume, the scent permeates the room. What law relates to this phenomenon?

Boyle's Law

Graham's Law

Charles' Law

None of these

Bottom of Form

Boyle's law

Boyle's law shows that, at constant temperature, the product of an ideal gas's pressure and volume is always constant. It was published in 1662. It can be determined experimentally using a pressure gauge and a variable volume container. It can also be found through the use of logic; if a container, with a fixed number of molecules inside, is reduced in volume, more molecules will hit the sides of the container per unit time, causing a greater pressure.

As a mathematical equation, Boyle's law is:

where P is the pressure (Pa), V the volume (m³) of a gas, and k₁ (measured in joules) is the constant from this equation—it is not the same as the constants from the other equations below.

Charles's law

Main article: Charles's law

Charles's Law, or the law of volumes, was found in 1678. It says that, for an ideal gas at constant pressure, the volume is directly proportional to the absolute temperature (in kelvin). Although this law remains constant, the formula for fusion strongly suggests that it is in fact, not an accurate measure at all.

The absolute temperature of the gas (in kelvin) and k₂ (in m³·K⁻¹) is the constant produced.

Gay-Lussac's law

Main article: Gay-Lussac's law

Gay-Lussac's law, or the pressure law, was found by Joseph Louis Gay-Lussac in 1809. It states that the pressure exerted on a container's sides by an ideal gas is proportional to the absolute temperature. P1 / T1 = P2 / T2

Avogadro's law

Main article: Avogadro's law

Avogadro's law states that the volume occupied by an ideal gas is proportional to the number of moles (or molecules) present in the container. This gives rise to the molar volume of a gas, which at STP is 22.4 dm³ (or litres). The relation is given by

where n is equal to the number of moles of gas (the number of molecules divided by Avogadro's Number).

Combined and ideal gas laws

Main article: Ideal gas law

The combined gas law or general gas equation is formed by the combination of the three laws, and shows the relationship between the pressure, volume, and temperature for a fixed mass of gas:

With the addition of Avogadro's law, the combined gas law develops into the ideal gas law:

where the constant, now named R, is the gas constant with a value of .08206 (atm∙L)/(mol∙K). An equivalent formulation of this law is: where

k is the Boltzmann constant (1.381×10⁻²³ J·K⁻¹ in SI units)

N is the number of molecules.

These equations are exact only for an ideal gas, which neglects various intermolecular effects (see real gas). However, the ideal gas law is a good approximation for most gases under moderate pressure and temperature.

This law has the following important consequences:

1. If temperature and pressure are kept constant, then the volume of the gas is directly proportional to the number of molecules of gas.
2. If the temperature and volume remain constant, then the pressure of the gas changes is directly proportional to the number of molecules of gas present.
3. If the number of gas molecules and the temperature remain constant, then the pressure is inversely proportional to the volume.
4. If the temperature changes and the number of gas molecules are kept constant, then either pressure or volume (or both) will change in direct proportion to the temperature.

Other gas laws

• Graham's law states that the rate at which gas molecules diffuse is inversely proportional to the square root of its density. Combined with Avogadro's law (i.e. since equal volumes have equal number of molecules) this is the same as being inversely proportional to the root of the molecular weight.

• Dalton's law of partial pressures states that the pressure of a mixture of gases simply is the sum of the partial pressures of the individual components. Dalton's Law is as follows:

where P_Total is the total pressure of the atmosphere, P_Gas is the pressure of the gas mixture in the atmosphere, and P_H2O is the water pressure at that temperature.

• Henry's law states that:
• At a constant temperature, the amount of a given gas dissolved in a given type and volume of liquid is directly proportional to the partial pressure of that gas in equilibrium with that liquid.

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HOW TO WRITE CHEMICAL FORMULAS

DIRECTIONS: If the answer to a question is No, go to the next similarly numbered or lettered question. If the answer is Yes, follow any directions listed and go on to the first subdivision. Once you have said Yes to a subdivision, all following subdivisions of that question are skipped unless they are preceded by an *. In this manner continue through questions 1 ---> 5 until the ions for the formula have been written. Then skip to number 6 and continue until the complete formula has been written.

1. Does the name of the compound include the word acid ?
   Write H (oxidation number +1) as the first element in the compound.
2. Does the name of the compound have the prefix hydro-?
   This means that the acid does not contain oxygen; therefore, the second part of the formula is either a monatomic ion (single element) or a polyatomic ion which does not contain oxygen (i.e. cyanide).
   Drop the prefix "hydro-", change the "-ic" ending to "-ide" and write this ion as the second part of the formula.
   Does the first part of the acid name end in -ic ?
   Change the "-ic" to "-ate" and write this polyatomic ion as the second part of the formula.
   Does the first part of the acid name end in -ous ?
   Change the -ous to -ite and write this polyatomic ion as the second part of the formula.
   Does the name of the compound have more than two words?
1. Does the last word end in -hydrate ?
   Write the formula for the compound listed before the word ending in -hydrate. (To do this continue on with section 2 (b) after you finish reading this section.) Follow this formula with a dot ^. , then the number for the Greek prefix attached to the word hydrate, ending with the formula for water.
   (Example: Copper (II) sulfate pentahydrate CuSO₄ ^. 5 H₂O)
2. *Does the name of the compound have the word hydrogen in the middle of the name?
   This indicates an acid salt. To write the formula and oxidation number for the negative polyatomic ion of an acid salt:
1. Write the formula for the polyatomic ion listed after the word hydrogen.
2. Write an H in front of the formula for this polyatomic ion. If the word hydrogen in the compound name contains a Greek prefix, write the number for the Greek prefix (if greater than 1) as the subscript for the Hyou just wrote. No Greek prefix indicates that there is only one possible acid salt for this polyatomic ion; and therefore, no subscript is required. (Remember a subscript one is understood and not written in compound formulas.)
3. To determine the oxidation for the negative polyatomic ion of an acid salt, add +1 for each hydrogen you added to the oxidation number of the original ion. (For example: PO₄^3- phosphate; H₂PO₄^1- dihydrogen phosphate) Now use this acid salt polyatomic ion as you would any other polyatomic ion in writing the formula of the compound listed.
3. Is the first word of the compound name an element or root of an element?
   Write the symbol for this element as the first part of the compound formula.
1. Is the first element a nonmetal?
   For a binary compound containing two nonmetals, use the Greek prefixes before the names of the elements to determine the number of atoms of each in the compound. If there is no Greek prefix for the first element, there is just one atom of that element in the formula.

Greek Prefixes	Number
mono-	1
di-	2
tri-	3
tetra-	4
penta-	5
hexa-	6
hepta-	7
octa-	8
nona-	9
deca-	10

2. 
   Note: If the name of the element begins with a vowel, the last vowel of the prefix is sometimes omitted.
   Complete entire formula using Greek prefixes.
   
   
3. Does the first word in the name of the compound end in -ous or -ic ?
   This means the metal ion (positive ion) in this compound has a varying oxidation number. [See Table of Common Cations with Varying Oxidation Numbers] For the -ous ending use the lower of the two oxidation numbers; for the -ic ending use the higher oxidation number. (Arsenic is an element with a name which ends in -ic. If the word arsenic in the compound name is followed by (III) , this means that it has an oxidation number of +3 and not +5 as the -ic ending alone would indicate.)
4. Is there a Roman numeral in parentheses in the middle of the compound name?
   This indicates a varying oxidation number for the first ion in the compound formula. Use the value of the Roman numeral as a positive oxidation number for the first element listed in the compound name.
5. Find the element on the Periodic Table. Locate the Roman numeral at the top of the column containing this element. Use the value of this Roman numeral as a positive oxidation number for the element. [Or see Table of Oxidation Numbers for Common Cations .]
3. Does the name of the compound end in -ide ?
1. Is the word ending in -ide the name of a polyatomic ion?

Hydroxide	OH1-		Ferrocyanide	Fe(CN)64-
Cyanide	CN1-		Ferricyanide	Fe(CN)63-

2. 
   If so, write the formula for this ion as the second part of the formula for the compound.
3. If the word ending in -ide is not a polyatomic ion, this means that the second part of the compound formula is a single element.
   Write the symbol for this element with its oxidation number. The oxidation number for the element written as the second part of the compound is determined by subtracting 8 from the Roman numeral located at the top of the column containing this nonmetal on the Periodic Table. Note: The oxidation number is negative. [Or see Table of Oxidation Numbers for Common Monatomic Anions.] [If you have written both the positive and the negative ion.
4. Does the name of the compound contain the name of a polyatomic ion?
   Identify the polyatomic ion or ions.
1. Is the polyatomic ion a positive ion? (Ammonium NH₄¹⁺)
   Write the formula for the polyatomic ion and its oxidation number as the first part of the compound formula.
   [If you have written both the positive and the negative ion
2. *Is the polyatomic ion a negative ion? Write the formula for the ion or the -ate form of the ion . [See Table of Common Polyatomic Ions .]
1. Does the polyatomic ion end in -ite ?
   Write one less oxygen than that given in the -ate form.
2. *Does the polyatomic ion have a prefix?
   Find the prefix in the following table.
   [Omit this section if the name of the ion copied from the The Table of Common Polyatomic Ions already contained the prefix.]

Prefix	Instructions
Per-	Add one oxygen to the-ate form.
Hypo-	Subtract one oxygen from the -ite form.
Bi-	Add one hydrogen (H) to the beginning of the polyatomic ion formula and add +1 to the oxidation number of the polyatomic ion.
Thio-	Substitute a sulfur (S) for one oxygen in the formula of the polyatomic ion.
Di-	Means the same as the prefix pyro- ; double the number of each element in the polyatomic ion and subtract one oxygen; double the oxidation number of the polyatomic ion and add +2.
Pyro-	[Same as prefix Di-]
Meta-	Subtract one oxygen from the polyatomic ion formula and add +2 to the oxidation number of the polyatomic ion.

6. Does the oxidation number of the positive ion have the same numerical value as that of the negative ion (The numbers are the same but the signs are opposite)?
   Ignore the oxidation numbers and write the formulas of the ions. Always write the positive ion first.
   For example: Ca²⁺ S^2- becomes CaS; Al³⁺ PO₄^3- becomes AlPO₄.
   Can the two different numerical values be reduced?
   Reduce the values, omit the signs, and crisscross these numbers, i.e. the reduced oxidation number of the positive ion minus its sign becomes the subscript for the negative ion, and the reduced oxidation number of the negative ion minus its sign becomes the subscript for the positive ion. The subscript one is understood and is not written in a formula. When subscripts have to be written with polyatomic ions, the polyatomic ion must be put in parentheses.
   For example: Pb⁴⁺ O^2- = Pb^4/2+ O^2/2- = Pb² O¹ and becomes PbO₂. Sn⁴⁺ SO₄^2- becomes Sn(SO₄)₂.
   
   
7. If the oxidation numbers cannot be reduced, crisscross the numbers omitting the signs and write the formula for the compound. Remember: When subscripts have to be written with polyatomic ions, the polyatomic ion is placed in parentheses; and when the subscript is 1, it is not written.
   For example: Al³⁺ SO₄^2- becomes Al₂(SO₄)₃. NH₄¹⁺ PO₄^3- becomes (NH₄)₃PO₄.

Chemical Formulas Review: Nomenclature and Formula Writing

Naming Simple Compounds

There are four naming systems you should familiarize yourself with to succeed on the SAT II Chemistry exam. The trick is recognizing which naming system to use. Here are the guidelines:

• If the compound starts with H, it is an acid. Use the naming acids rules.
• If the compound starts with C and contains quite a few H’s and perhaps some O’s, it is organic. Use the naming organic compounds rules.
• If the compound starts with a metal, it is most likely ionic. Use the naming binary ionic compounds rules.
• If the compound starts with a nonmetal other than H or C, use the naming binary molecular compounds rules.

It is also essential that you memorize some common polyatomic ions. Polyatomic ions behave as a unit. If you need more than one of them, enclose them in parentheses when you write formulas. You need to know their names, formulas, and charges. If you learn the nine that follow, you can get many others from applying two simple patterns.

Name of polyatomic ion	Formula and charge
Ammonium ion	NH4+
Acetate ion	C2H3O2-
Cyanide ion	CN-
Hydroxide ion	OH-
Nitrate ion	NO3-
Chlorate ion	ClO3-
Sulfate ion	SO42-
Carbonate ion	CO32-
Phosphate ion	PO43-

• Pattern 1: The -ates “ate” one more oxygen than the -ites and their charge doesn’t change as a result! For instance, if you know nitrate is NO₃^-,then nitrite is NO₂^-.If you know phosphate is PO₄^3-,then you know phosphite is PO₃^3-.You can also use the prefixes hypo- and per- with the chlorate series. Perchlorate, ClO₄^-,was really “hyper and ate yet another oxygen” when compared to chlorate, ClO₃^-.Hypochlorite is a double whammy: it is -ite and therefore “ate” one less oxygen than chlorate and it is hypo-, which means “below,” so it “ate” even one less oxygen than plain chlorite, so its formula is ClO^-. You can also substitute the other halogens for Cl and make additional sets of the series.
• Pattern 2: The -ates with charges less than negative 1 (that is, ions with charges of -2, -3, etc.) can have an H added to them to form new polyatomic ions. For each H added, the charge is increased by a +1. For instance, CO₃^2-can have an H added and become HCO₃^-.HCO₃^-is called either the bicarbonate ion or the hydrogen carbonate ion. Since phosphate is -3, it can add one or two hydrogens to make two new polyatomic ions, HPO₄^2-and H₂PO₄^-.These are named hydrogen phosphate and dihydrogen phosphate, respectively. If you keep adding hydrogen ions until you reach neutral, you’ve made an acid! That means you need to see the naming acids rules.
• Pattern 3: The following periodic table will also come in handy. Notice there are simple patterns for determining the most common oxidation states of the elements based on their family’s position in the periodic table. Notice the 1A family is +1, while the 2A family is +2; then skip across to the 3A family and see that aluminum is +3. Working backward from the halogens, or 7A family, the oxidation states are most commonly -1, while the 6A family is -2, and the 5A family is -3. The 4A family is “wishy-washy”: they can be several oxidation states, with the most common being +4.

Naming Acids

How do you know it’s an acid? The compound’s formula begins with an H, and water doesn’t count! Naming acids is extremely easy if you know your polyatomic ions. There are three rules to follow:

• H + element: When the acid has only an element following the H, use the prefix hydro-, followed by the element’s root name and an -ic ending. HCl is hydrochloric acid; H₂S is hydrosulfuric acid. When you see an acid name beginning with hydro-, think: Caution, element approaching! HCN is an exception since it is a polyatomic ion without oxygen, so it is named hydrocyanic acid.
• H + -ate polyatomic ion: If the acid has an -ate polyatomic ion after the H, that makes it an -ic acid. H₂SO₄ is sulfuric acid.
• H + -ite polyatomic ion: When the acid has an -ite polyatomic ion after the H, that makes it an -ous acid. H₂SO₃ is sulfurous acid.

Acids have enough H⁺ added to the anion to make the compound neutral. Supply either the acid’s name or its formula to complete the table below:

Acid formula	Acid name
HCl
	Hypochlorous acid
	Chlorous acid
	Chloric acid
HNO3	Hyperchloric acid (or perchloric acid)
H3PO4	Hydrobromic acid
H3PO3	Hydrocyanic acid
HC2H3O2	Carbonic acid
HF	Hydroiodic acid

Naming Organic Compounds

How do you know it’s organic? The formula will start with a C followed by H’s. Most of the organic carbons you will encounter will be either hydrocarbons or alcohols, and luckily for you, these are the simplest of all to name. Learn the list of prefixes in the table following this section: they correspond to the number of carbons present in the compound. The following silly statement will help you remember the order of the first four prefixes since they are not ones you are familiar with: “Me eat peanut butter.” This corresponds to meth-, eth-, prop-, and but-, which correspond to one, two, three, and four carbons, respectively.

Now that we have a stem, we need an ending. There are three common hydrocarbon endings; the ending changes depending on the structure of the molecule:

• -ane = alkane (all single bonds and saturated); C_nH_2n+2; saturated: it contains the maximum number of H’s
• -ene = alkene (contains double bond, unsaturated); C_nH_2n
• -yne = alkyne (contains triple bond, unsaturated); C_nH_2n-2; polyunsaturated: it contains more than one double or triple bond

For any hydrocarbon, you can remove one H and replace it with a hydroxyl group, or —OH group, to form an alcohol. Do not be fooled—this looks like a hydroxide group but isn’t! The OH does not make this hydrocarbon an alkaline or basic compound, nor do you name it as a hydroxide! C₂H₆ is ethane, while C₂H₅OH is ethanol. Fill in the missing formulas and names for each compound in the table:

No. of carbon atoms = n	Prefix or stem	-ane CnH2n+2	-ene CnH2n	-yne CnH2n–2	-anol CnH2n+1 + OH
1	meth-		Must have 2 carbons		CH3OH
2	eth-
3	prop-		C3H6
4	but-
5	pent-	C5H12
6	hex-
7	hept-				C7H15OH
8	oct-			C8H14
9	non-
10	dec-

Naming Binary Ionic Compounds

How will you know a compound is ionic? You’ll know because the formula will begin with a metal cation or the ammonium cation. Formulas often end with a polyatomic anion. If only two elements are present, they are usually from opposite sides of the periodic table, like in KCl. If the metal is one of the transition metals, be prepared to use a Roman numeral to indicate which oxidation state the metal is exhibiting. Silver, cadmium, and zinc are exceptions to the Roman numeral rule! First, let’s name the ions.

Naming positive ions (usually metals)

• Monatomic, metal, cation: simply the name of the metal from which it is derived. Al³⁺ is the aluminum ion (these are often referred to as group A metals).
• Transition metals form more than one ion; Roman numerals (in parentheses) follow the ion’s name. Cu²⁺ is copper (II) ion. Exception: mercury (I) is Hg₂²⁺, that is, two Hg⁺ bonded together covalently.
• NH₄⁺is ammonium.
• Roman numerals are not usually written with silver, cadmium, and zinc. Arrange their symbols in alphabetical order—the first one is 1+ and the other two are 2+.

Naming negative ions (usually nonmetals or polyatomic ions)

• Monatomic, nonmetal, anion: add the suffix -ide to the stem of the nonmetal’s name. Halogens are called the halides. Cl^- is the chloride ion.
• Polyatomic anion: you must memorize the polyatomic ion’s name. NO₂^-is the nitrite ion.

Subscript	Prefix
1	mono- (usually used only on the second element, such as carbon monoxide or nitrogen monoxide)
2	di-
3	tri-
4	tetra-
5	penta-
6	hexa-
7	hepta-
8	octa-
9	nona-
10	deca-

Naming ionic compounds: The positive ion name is given first (remember, if it’s a transition metal, the Roman numeral indicating its charge is part of its name), followed by the name of the negative ion. No prefixes are used.

Naming Binary Molecular Compounds

How will you know if it’s a molecular compound? Well, it will be a combination of nonmetals, both of which lie near each other on the periodic table. Use the following set of prefixes, and don’t forget the -ide ending to the name.

If the second element’s name begins with a vowel, the a at the end of the prefix is usually dropped. N₂O₅ is dinitrogen pentoxide, not dinitrogen pentaoxide. PCl₅ is phosphorous pentachloride, not phosphorous pentchloride.

Nomenclature for Ionic Compounds

Ionic compounds consist of cations (positive ions) and anions (negative ions). The nomenclature, or naming, of ionic compounds is based on the names of the component ions. Here are the principal naming conventions for ionic compounds, along with examples to show how they are used:

• Roman Numerals
  A Roman numeral in parentheses, followed by the name of the element, is used for elements that can form more than one positive ion. This is usually seen with metals. You can use a chart to see the possible valences for the elements.

Fe²⁺ Iron (II)
Fe³⁺ Iron (III)
Cu⁺ Copper (I)
Cu²⁺ Copper (II)

• -ous and -ic
  Although Roman numerals are used to denote the ionic charge of cations, it is still common to see and use the endings -ous or -ic. These endings are added to the Latin name of the element (e.g., stannous/stannic for tin) to represent the ions with lesser or greater charge, respectively. The Roman numeral naming convention has wider appeal because many ions have more than two valences.

Fe²⁺ Ferrous
Fe³⁺ Ferric
Cu⁺ Cuprous
Cu²⁺ Cupric

• -ide
  The -ide ending is added to the name of a monoatomic ion of an element.

H^- Hydride
F^- Fluoride
O^2- Oxide
S^2- Sulfide
N^3- Nitride
P^3- Phosphide

• -ite and -ate
  Some polyatomic anions contain oxygen. These anions are called oxyanions. When an element forms two oxyanions, the one with less oxygen is given a name ending in -ite and the one with more oxgyen is given a name that ends in -ate.

NO₂^- Nitrite
NO₃^- Nitrate
SO₃^2- Sulfite
SO₄^2- Sulfate

• hypo- and per-
  In the case where there is a series of four oxyanions, the hypo- and per- prefixes are used in conjunction with the -ite and -ate suffixes. The hypo- and per- prefixes indicate less oxygen and more oxygen, respectively.

ClO^- Hypochlorite
ClO₂^- Chlorite
ClO₃^- Chlorate
ClO₄^- Perchlorate

• bi- and di- hydrogen
  Polyatomic anions sometimes gain one or more H⁺ ions to form anions of a lower charge. These ions are named by adding the word hydrogen or dihydrogen in front of the name of the anion. It is still common to see and use the older naming convention in which the prefix bi- is used to indicate the addition of a single hydrogen ion.

HCO₃^- Hydrogen carbonate or bicarbonate
HSO₄^- Hydrogen sulfate or bisulfate
H₂PO₄^- Dihydrogen phosphate

Breakthrough in Chemistry

Two superheavy elements, elements 113 and 115, were recently synthesized through a collaborative effort between scientists from the Physical and Life Sciences Directorate at the Lawrence Livermore National Laboratory and researchers from the Joint Institute for Nuclear Research at the Flerov Laboratory for Nuclear Reactions in Dubna, Russia. Two isotopes of element 115 survived 30-80 milliseconds before decaying into isotopes of element 113 that survived approximately ten times longer prior to decaying themselves. Following a series of alpha-decays, the element 115 atoms decayed into long-lived isotopes (multiple hours) of element 105 (Db). The great-great-great granddaughter Db isotopes were also chemically identified in subsequent experiments.

1. What is a heavy element?

A heavy element is an element with an atomic number greater than 92. The first heavy element is neptunium (Np), which has an atomic number of 93. Some heavy elements are produced in reactors, and some are produced artificially in cyclotron experiments.

2. What is a superheavy element?

The definition of superheavy elements (SHE) varies among different groups of people. We use the term term SHE to refer to those elements with an atomic number greater than or equal to 112. The first superheavy element is element 113, which has been recently discovered by a collaboration of scientists from the Lawrence Livermore National Laboratory and the Joint Institute of Nuclear Research in Russia. Like some of the heavy elements, superheavy elements are produced artificially in cyclotron experiments.

3. What is an atomic number?

The atomic number refers to the number of protons in an element’s nucleus. Each element has a unique atomic number and is known by that number until it receives an official name. For example, the two new superheavy elements 113 and 115 have 113 and 115 protons, respectively, in their nuclei.

4. How are new elements discovered?

Several experimental techniques have been used to make new chemical elements. Some of these include heavy ion transfer reactions, cold or hot fusion evaporation reactions, neutron capture reactions, light-ion charged particle induced reactions, and even nuclear explosions. These techniques each have advantages and disadvantages making them suitable for studying nuclei in certain regions.

The types of nuclear reactions that have been successfully used to produce new elements in the last decade are cold fusion reactions and hot fusion reactions. Cold fusion reactions use beam and target nuclei that are closer to each other in mass in order to produce a compound nucleus (the complete fusion of one target nucleus with one beam nucleus) with generally lower excitation energy that typically requires evaporation of one or no neutrons. This generates fewer neutron-rich isotopes of an element that have higher survival probabilities with respect to fission, but have lower fusion probabilities. An example of this type of reaction is ⁷⁰Zn + ²⁰⁸Pb → ²⁷⁷112 + 1n with a cross-section of ~1 picobarn.

Because the 112 isotope ultimately decays by a emission to known nuclei [namely isotopes of elements 102 (No) and 104 (Rf)], identification of this element is straightforward. Hot fusion reactions use more asymmetric beam and target nuclei, produce a compound nucleus with generally higher excitation energy that typically requires evaporation of three to five neutrons, generate more neutron-rich isotopes of an element, have lower survival probabilities with respect to fission, but have higher fusion probabilities. An example of this type of reaction is ⁴⁸Ca + ²⁴⁴Pu → ²⁸⁸114 + 4n with a cross-section of ~1 pb. Because of the neutron-richness of this isotope of element 114, it never subsequently decays to any known isotope, and thus its identification is more problematic. Cold fusion reactions have been successful in producing elements 104—112 and hot fusion reactions have recently provided evidence for elements 113—116 and 118.

MIXTURES

Mixtures are classified into two on basis of the nature of the solvents n solutes.

1. Homogenous mixtures: Homogenous mixtures are those in which the solute n solvent are not seen as two separate phases but as one continuous phases. For example, consider a solution of salt in water.
2. Heterogenous mixtures: Heterogenous mixtures are those in which the solute n solvent are distinctly separable into two phases. For example, consider a mixture of oil and water.

On basis of physical state of solute and solvents, mixtures are classified into nine types:

1. Solid in Solid: metal alloys, etc.
2. Solid in Liquid: solution of sugar in water, etc.
3. Solid in Gas: smoke particles suspended in air, etc.
4. Liquid in Solid: paste, colloids, etc.
5. Liquid in Liquid: solution of alcohol in water.
6. Liquid in Gas: water droplets suspended in air.
7. Gas in Solid: hydrogen gas adsorbed on platinum surface.
8. Gas in Liquid: aerated drinks
9. Gas in Gas: air

Saturated, Unsaturated and Supersaturated

Solubility is defined as the maximum amount of solute dissolved by a given amount of solvent at a definite temperature.

The solubility of the given substances in a given solute is temperature-dependent.

Solution containing the maximum amount of solute at room temperature is saturated. When more solute is added into the solution the solute will no longer dissolve.

If the solution contains the maximum amount of solute at an elevated temperature the solution is supersaturated. When more solute is added into the solution, crystals will form.

If the solution contains less quantity of solute than what can be dissolved at room temperature it is unsaturated. When more solute is added into solution the solute dissolves.

Solutions

A solution is defined as a clear and homogeneous mixture of a solute in a solvent.

Common solutions are: salt and water, alcohol and water, or sugar and water. These mixtures are all clear and homogeneous.

The solute is the substance that dissolves; the solvent is the substance that does the dissolving.

In a mixture of salt and water, the salt is the solute and the water is the solvent.

In a mixture of alcohol and water, the alcohol is the solute and the water is the solvent.

Solutes Some solids when added to water do not dissolve in the water. These solids are said to be insoluble. They are known as insoluble solutes. Both iodine and chalk are insoluble solutes in water. An insoluble solute will settle out of the mixture. Insoluble solutes are usually found at the bottom of the container as a precipitate. Can you see the chalk and the iodine precipitate in the pictures to the right? A mixture containing an insoluble solute is classified as a suspension, not a solution.

When solids do dissolve in water they are said to be soluble. They are known as soluble solutes. Try saying soluble solutes out loud 10 times as fast as you can! Could you do it without slurring your words?

 Substances other than water can be used as solvents. A common solvent other than water is alcohol. There are some solutes that are soluble in water and insoluble in alcohol. And, then there are some solutes that are soluble in alcohol and insoluble in water.

Examples:	Iodine is insoluble in water but soluble in alcohol
	Salt is soluble in water but insoluble in alcohol

Properties of Matter

Extrinsic Property- is a property that depends on the amount or quantity of the material.
- also known as the "Extensive Physical Property".


Examples of the Extrinsic Property:

1.) Length 4.) Width 7.) Area
2.) Mass 5.) Height 8.) Thickness
3.) Volume 6.) Circumference 9.) Weight



Intrinsic Property- is a property that depends on the kind or quality of the material.
- also known as the " Intensive Physical Property".

Examples of Intrinsic Property:


1.) Density 10.) Specific heat
2.) Texture 11.) Malleability
3.) Odor 12.) Ductility
4.) Taste 13.) Solubility
5.) Hardness 14.) Magnetic properties
6.) Boiling point 15.) Surface tension
7.) Melting point 16.) Gas diffusion
8.) Electrical conductivity 17.) Color
9.) Freezing point 18.) Metallic luster

DEFINITION AND CLASSIFICATION OF COLLOIDS

The term colloidal refers to a state of subdivision, implying that the molecules or polymolecular particles dispersed in a medium have at least in one direction a dimension roughly between 1 nm and 1µm, or that in a system discontinuities are found at distances of that order. It is not necessary for all three dimensions to be in the colloidal range: fibers in which only two dimensions are in this range, and thin films, in which one dimension is in this range, may also be classified as colloidal. Nor is it necessary for the units of a colloidal system to be discrete: continuous network structures, the basic units of which are of colloidal dimensions also fall in this class (e.g. porous solids, gels and foams).

A colloidal dispersion is a system in which particles of colloidal size of any nature (e.g. solid, liquid or gas) are dispersed in a continuous phase of a different composition (or state).

The name dispersed phase for the particles should be used only if they have essentially the properties of a bulk phase of the same composition.

The term colloid may be used as a short synonym for colloidal system. The size limits given above are not rigid since they will depend to some extent on the properties under consideration. This nomenclature can be applied to coarser systems, especially when a gradual transition of properties is considered.

The description of colloidal systems often requires numbering of the components or constituents. It is felt that a fixed rule of numbering is unnecessarily restrictive. However, the author should make clear in all cases how he is numbering and in particular whether he is numbering by independent thermodynamic components (all neutral) or by species or constituents, of which some may be ionic, and which may be related by equilibrium conditions or by the condition of electroneutrality. In comparing English and French, it should be realized that the English word `component' is usually equivalent to the French `constituent' and the English `constituent' to the French `composant'.

A fluid colloidal system composed of two or more components may be called a sol, e.g. a protein sol, a gold sol, an emulsion, a surfactant solution above the critical micelle concentration (cf. §1.6), an aerosol.

In a suspension solid particles are dispersed in a liquid; a colloidal suspension is one in which the size of the particles lies in the colloidal range.

In an emulsion liquid droplets and/or liquid crystals are dispersed in a liquid. In emulsions the droplets often exceed the usual limits for colloids in size. An emulsion is denoted by the symbol O/W if the continuous phase: is an aqueous solution and by W/O if the continuous phase is an organic liquid (an `oil'). More complicated emulsions such as O/W/O (i.e. oil droplets contained within aqueous droplets dispersed in a continuous oil phase) are also possible. Photographic emulsions, although colloidal systems, are not emulsions in the sense of this nomenclature.

A latex (plural = latices or latexes) is an emulsion or sol in which each colloidal particle contains a number of macromolecules.

A foam is a dispersion in which a large proportion of gas by volume in the form of gas bubbles, is dispersed in a liquid, solid or gel. The diameter of the bubbles is usually larger than 1 , but the thickness of the lamellae between the bubbles is often in the usual colloidal size range.

The term froth has been used interchangeably with foam. In particular cases froth may be distinguished from foam by the fact that the former is stabilized by solid particles (as in froth-flotation q.v.) and the latter by soluble substances.

Aerosols are dispersions in gases. In aerosols the particles often exceed the usual size limits for colloids. If the dispersed particles are solid, one speaks of aerosols of solid particles, if they are liquid of aerosols of liquid particles. The use of the terms solid aerosol and liquid aerosol is discouraged. An aerosol is neither `solid' nor `liquid' but, if anything, gaseous.

A great variety of terms such as dust, haze, fog, mist, drizzle, smoke, smog are in use to describe aerosols according to their properties, origin, etc. Of these only the terms fog and smoke are included in this nomenclature.

A fog is an aerosol of liquid particles, in particular a low cloud.

A smoke is an aerosol originating from combustion, thermal decomposition or thermal evaporation. Its particles may be solid (magnesium oxide smoke) or liquid (tobacco smoke).

A gel is a colloidal system with a finite, usually rather small, yield stress. Materials such as silica gel which have passed a gel stage during preparation, are improperly called gels.

The term xerogel is used for such dried out open structures; and also for dried out compact macromolecular gels such as gelatin or rubber.

The term aerogel is used when the openness of the structure is largely maintained.

Colloidal dispersions may be lyophobic (hydrophobic, if the dispersion medium is an aqueous solution) or lyophilic (hydrophilic). Lyophilic sols are formed spontaneously when the dry coherent material (e.g. gelatin, rubber, soap) is brought in contact with the dispersion medium, hence they are thermodynamically more stable than in the initial state of dry colloid material plus dispersion medium. Lyophobic sols (e.g. gold sol) cannot be formed by spontaneous dispersion in the medium. They are thermodynamically unstable with respect to separation into macroscopic phases, but they may remain for long times in a metastable state.

Lyophilic sols comprise both association colloids in which aggregates of small molecules are formed reversibly and macromolecules in which the molecules themselves are of colloidal size.

Mixtures of lyophobic and lyophilic colloids, may form protected lyophobic colloids (cf. §1.5).

The terms lyophilic (hydrophilic, lipophilic, oleophilic, etc.) and lyophobic, (lipophobic, etc.) may also be used to describe the character of interaction of a particular atomic group with the medium. In this usage the terms have the relative qualitative meaning of `solvent preferring' (water-preferring, fat-preferring etc.) and `solvent rejecting' (water-rejecting, fat-rejecting, etc.) respectively.

The terms `solvent preferring' or `solvent rejecting' always refer to a differential process usually in the sense of preferring the solvent above itself or preferring itself above the solvent but sometimes preferring one solvent (e.g. water) above another (e.g. oil).

A colloidal electrolyte is an electrolyte which gives ions of which at least one is of colloidal size. This term therefore includes hydrophobic sols, ionic association colloids, and polyelectrolytes.

Ions of low relative molecular mass, with a charge opposite to that of the colloidal ion, are called counterions; if their charge has the same sign as that of the colloidal ion, they are called co-ions.

A polyelectrolyte is a macromolecular substance which, on dissolving in water or another ionizing solvent, dissociates to give polyions (polycations or polyanions)--multiply charged ions--together with an equivalent amount of ions of small charge and opposite sign. Polyelectrolytes dissociating into polycations and polyanions, with no ions of small charge, are also conceivable. A polyelectrolyte can be a polyacid, a polybase, a polysalt or a polyampholyte.

If all particles in a colloidal system are of (nearly) the same size the system is called monodisperse; in the opposite cases the systems are heterodisperse.

If only a few particle-sizes occur in a colloidal system the system is paucidisperse and if many particle-sizes occur polydisperse.

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In addition to you notes,  I have provided you with these review materials in preparation for your mid term examination. Administration of examination will be on the scheduled time. Secure your  examination permit as soon as possible. Type of test will be multiple choice. Number of test items will be 100. Good Luck!

                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                

                                                                                                                                                                    Instructor