CHEM 120: Introduction to Inorganic Chemistry

Instructor: Upali Siriwardane (Ph.D., Ohio State University)

CTH 311, Tele: 257-4941, e-mail: upali@chem.latech.edu

Office hours: 10:00 to 12:00 Tu & Th ; 8:00-9:00 and 11:00-12:00 M,W,& F

Chapters Covered and Test dates

Tests will be given in regular class periods from 9:30-10:45 a.m. on the following days:

September 22,     2004 (Test 1): Chapters 1 & 2

October 8,           2004(Test 2): Chapters 3, & 4

October 20,         2004 (Test 3): Chapter 5 & 6

November 3,        2004 (Test 4): Chapter 7 & 8

November 15,      2004 (Test 5): Chapter 9 & 10

November 17,      2004 MAKE-UP: Comprehensive test (Covers all chapters

Grading:

[( Test 1 + Test 2 + Test3 + Test4 + Test5)] x.70 + [ Homework + quiz average] x 0.30 = Final Average

                                            5

Chapter 6. States of Matter: Gases, Liquids, and Solids

Describe the behavior of gases : Boyle's law, Charles's law, combined gas law, Avogadro's law, the ideal gas law, and Dalton's law.

2. Use gas law equations to calculate conditions and changes in conditions of gases.

3. Describe the major points of the kinetic molecular theory of gases.

4. Explain the relationship between the kinetic molecular theory and the physical properties of macroscopic quantities of gases.

5. Describe properties of the liquid state.

6. Describe the processes of melting, boiling, evaporation, and condensation.

7. Describe the dipolar attractions known collectively as London dispersion (van der Waals) forces.

8. Describe hydrogen bonding and its relationship to boiling and melting

temperatures.

9. Relate the properties of the various classes of solids (ionic, covalent,

molecular, and metallic) to the structure of these solids.

States of matter

By changing the temperature (and pressure) all matter can exist as a solid, as a liquid and as a gas.

There are forces of attraction (which we learn about later) btn cmpds that determine what physical state (gas, liquid, solid) we find the cmpd in at a given temperature.

"Temperature gives molecules kinetic energy"

Temperature gives molecules kinetic energy. ______ the temp the ________ the kinetic energy.

If the strength of attractive forces btn molecules is much larger than the kinetic energy due to temp the cmpd will be a ________

If the molecules’ kinetic energy due to temp is much greater than the attractive forces btn molecules the cmpd will be a _______

If the attractive forces and the energy due to temp are similar the cmpd will be a _______

Slide 6

"Gas properties:"

Gas properties:

"Liquid properties:"

Liquid properties:

"Solid properties:"

Solid properties:

.

"4."

4. In general for the same substance density of a solid > density of a liquid > density of a gas

For water density_liquid > density_solid (ice floats)

See table 6.1

The gaseous state

We are going to describe a gas in terms of the pressure (P) it exerts, the volume (V) it occupies and its temperature (T).

Pressure is a

We live at the bottom of a sea of gas molecules which are constantly hitting us and exerting pressure on us.

Slide 12

"The downward force on any..."

The downward force on any surface area (say 1 in²)due to “air” is equal to the mass of the column of air above the area and is 14.7psi (lb/in²).

We measure the pressure of the atmosphere with a

Slide 14

"P_air = P_Hg in the..."

P_air = P_Hg in the barometer tube. The downward pressure of the mercury in the column is balanced by the outside atmospheric pressure pressing down on the mercury in the dish.

We define one atmosphere as the atmospheric pressure which

"1 atm ="

1 atm =

(1 torr = 1 mm Hg)

Express 528 mm Hg in atm

Express 2.86 atm in mm Hg and torr.

Objectives

4 easily measured macroscopic properties: V, T, P, n (# moles)

Now we want to develop a mathematical relationship btn P,V,T and the no. of moles (n) of a gas.

Boyle’s law

Boyle (1660) did some experiments that showed as the pressure applied to a gas increases, the volume occupied by the gas decreases as long as the temperature and amt of gas is held constant.

Slide 19

"or P µ 1/V and..."

or P µ 1/V and V µ 1/P

PV = k₁ where k₁ is a proportionality constant that is

P_iV_i = k₁ and P_fV_f =k₁ so

P_iV_i = P_fV_f at the same temp and no.moles of gas

"Gases follow Boyle’s law best..."

Gases follow Boyle’s law best (PV=k) at

.

complete P_i(atm)    P_f(atm)       V_i(L)         V_f(L)

         1.0         0.50            ?                0.30

         1.0         2.0              0.75            ?

What happens to the volume if you triple the pressure at constant temp and no. moles?

Charles’ Law, T and V

Charles, a hot air balloonist, (1800’s) investigated how V and T (temperature in K) were related.

He found that as the temperature of the gas increased, the volume occupied by the gas also increased as long as the pressure and amt of the gas were held constant.

Slide 23

"or V µ T"

or V µ T and V = k₂T where k₂ is a proportionality constant that depends on the

Remember to convert from ^oC to K

Charles’ Law

V = k₂T

V/T = k₂

k₂ = proportionality constant

independent of identity of gas

requires constant P and n

V_i/T_i = k₂ and V_f/T_f = k₂ so

V_i/T_i = V_f/T_f

excellent approximation at

"What happens to the volume..."

What happens to the volume when the temp in Kelvin is tripled at constant P and n?

Avogadro’s Law, V and n

Avogadro found that the volume of a gas increased as the amt of the gas increased when the pressure and temp were held constant. (balloon)

V µ n or V = k₃n direct relationship

"V µ n"

V µ n

V = k₃n

V/n = k₃

V_i/n_i = V_f/n_f

holds best at

Upshot of Avogadro’s Law

Equal volumes of gases under the same conditions of temp and pressure contain equal nos. of particles.

Equal moles of all gases under the same conditions of temp and pressure have the same volume.

The Ideal Gas Law

Boyle: V µ 1/P

Charles: V µ T

Avogadro: V µ n

"An ideal gas obeys the..."

An ideal gas obeys the gas laws we have developed. A real gas may deviate somewhat from these laws. But under conditions of _____________________, these laws are obeyed. The reason for this will be discussed later.

"STP (standard temp and..."

STP (standard temp and pressure)

It is found that 1 mol of a gas occupies a volume of

Substituting the molar volume at STP in PV=nRT

"we get"

we get

Molar volume

V of one mole of gas at STP = 22.4 L

Same V regardless of identity of gas!

but

22.4 L of N₂

22.4 L of CH₄(g)

Gas densities

d =

At STP

1 mol of H₂ has a mass of 2.0 g so d_H2 =

1 mol of O₂ has a mass of 32.0 g so d_O2 =

1 mol of CO has a mass of 28.0 g so d_CO =

"The ideal gas law contains..."

The ideal gas law contains all the other laws.

"The temp has to be..."

The temp has to be in

In the comparative laws (Boyle’s, Charles’, etc) pressure and volume just have to be in the same units. n has to be in moles

In the ideal gas law the units are as specified before.

Problems

A sample of nitrogen gas kept in a container of volume 2.3L and at a temp of 32^oC exerts a pressure of 4.7 atm. Calc the no. of moles and the mass of gas present.

"A balloon has a volume..."

A balloon has a volume of 43.0L at 20^oC. What is its volume at -5^oC?

A syringe has a volume of 10.0mL at 14.7psi. If the tip is blocked so that air can’t escape, what pressure is required to decrease the volume to 2.00mL?

If 20.0g of N₂gas has a volume of 4.00L and a pressure of 6.00atm, what is its temp?

"Which sample contains more molecules"

Which sample contains more molecules: 2.0L of CO₂ at 300K and 500 mm Hg or 1.5L of N₂ at 57^oC and 760 mm Hg? Which sample weighs more?

An aerosol can has an internal pressure of 3.75atm at 25^oC. What temp is required to raise the pressure to 16.6atm?

"A compressed-air tank carried by..."

A compressed-air tank carried by scuba divers has a volume of 8.0L and a pressure of 140 atm at 20^oC. What is the volume of air in the tank at 0^oC and 1.00atm pressure (STP)?

Cyclopropane. C₃H₆, is used as a general anesthetic. If a sample of cyclopropane is stored in a 2.00 L container at 10.0 atm and 25.0^oC is transferred to a 5.00 L container at 5.00 atm, what is its resulting temp?

"What is the effect on..."

What is the effect on a gas if you simultaneously:

a) halve its pressure and double its Kelvin temp

b) double its pressure and double its Kelvin tempereature.

"What volume will 818 g..."

What volume will 818 g of sulfur hexafluoride gas occupy if the temperature and pressure of the gas are 128^oC and 9.4 atm?

At what temp will 2.00 mol He fill a 2.00 L container at STP?

"6.34:"

6.34: How many grams of helium must be added to a balloon containing 8.00 g of helium gas to double its volume. Assume no temp or pressure change.

Dalton’s Law of Partial Pressures

Dalton (1803) said in a mixture of gases, each gas exerts a pressure as if it were present alone in the container. The pressure each gas exerts is called

Dalton’s Law of Partial Pressures

For gas mixtures

Partial Pressure –pressure of an individual gas component in a mixture

Dalton’s Law of Partial Pressure – total pressure of a mixture of gases is the sum of the pressures that each gas would exert if it were present alone

"The mixture of gases as..."

The mixture of gases as well as each gas obeys the ideal gas law and all of the other laws.

"The partial pressure of CH₄(g"

The partial pressure of CH₄(g) is 0.225atm and C₂H₆(g) is 0.165 atm in a mixture of the two gases. What is the total pressure?

A gas mixture has three components, N₂, O₂ and He. If the total pressure of the mixture is 0.78 atm and the partial pressure of N₂ and He are 0.40 atm and 0. 18 atm respectively, what is the partial pressure of the O₂ in the mixture?

Kinetic Molecular Theory of Gases

There are several basic hypotheses that are used to explain the behavior of gases.

1.Volume occupied by gas molecules themselves is negligible compared to the total volume occupied by the gas itself. (Gas molecules are though of as point masses: have mass but occupy no volume.)

"2.The molecules of a gas..."

2.The molecules of a gas are in constant, rapid, random straight line motion (Brownian motion) with no attractive forces btn the the molecules.

3.The collisions the molecules make with themselves and with the walls of the container are elastic collisions. In other words energy is transferred from one molecule to another in a collision but the total energy of the molecules stays the same.

"4."

4. At a given time the gas molecules have different speeds and different kinetic energies but the average kinetic energy of all the molecules of the gas is directly proportional to the Kelvin temperature(T).

KE_average µ T or

KE_average = cT where c is a constant

Note that as

Gases that obey these assumptions are known as

How good are these assumptions?

Zero volume?

No attractive forces?

"How explain compressibility,"

How explain compressibility, expand, low density, diffusion

KE = 1/2mv²

At the same temp, molecules with

What are these forces?

Back to end of chapter 4 and review polar vs nonpolar

Intermolecular forces

Now what are these intermolecular forces we mentioned earlier.

Intermolecular forces are forces btn different molecules. Intramolecular forces are forces btn atoms in a bond (of the order of 200-500 kJ)--generally much stronger than intermolecular forces.

"Stronger intermolecular force,"

Stronger intermolecular force, the _______ the boiling and melting points

What are these forces?

I. ion-ion forces:

"II.Dipole-dipole forces:"

II.Dipole-dipole forces: forces that operate when have ______ molecules. In general, the more polar the molecule (larger the difference in electronegativities), the stronger the forces.

These forces (dipole-dipole) are of the order of 5 to 20 kJ/mol. Cmpds that have these forces (dipole-dipole) are frequently

Slide 58

"III."

III. London (dispersion) forces: used to explain intermolecular forces in

Electrons in molecules are constantly moving.

On the average, in a nonpolar molecule the electrons are evenly distributed leading to an overall equal sharing throughout.

But since electrons are moving, at some instance in time there is an unequal distribution and an

"This instantaneous dipole induces a..."

This instantaneous dipole induces a dipole in neighboring molecules, creating an interaction btn molecules.

This interaction is relatively weak (0.1-5 kJ).

London and dipole-dipole forces are known collectively a

Slide 61

"Remember as strength of forces..."

Remember as strength of forces increase have higher m and b pts.

Therefore

and

and

Notice that we are comparing like species,

But what about HF, HCl, HBr, HI and H₂O, H₂S, H₂Se, H₂Te and NH₃, PH₃, AsH₃ and SbH₃.

Slide 63

"Explain these anomalies by a..."

Explain these anomalies by a “new” force called

Requirements for hydrogen bonding:

Slide 65

"Water forms 4 hydrogen bonds..."

Water forms 4 hydrogen bonds per molecule, HF and NH₃ only one.

"Dimethyl ether (CH₃OCH₃)"

Dimethyl ether (CH₃OCH₃) and ethanol (C₂H₅OH) have the same formula (C₂H₆O) but the b pt of the ehter is -25^oC and of the ethanol 78^oC. Explain.

Which of these form hydrogen bonds?

CH₃OH

C₂H₄

CH₃NH₂

HCN

NH₄+

"In general ionic forces the..."

In general ionic forces the strongest, then hydrogen bonding, dipole-dipole and lastly dispersion for species of similar molar mass.

N₂ (bpt -195^oC)    O₂ (bpt -183^oC)

N₂ (bpt -195^oC)    CO (bpt -190^oC) H₂O (bpt 100^oC)

CH₃F (-141.8^oC)   CCl₄ (-23^oC)

NaCl (801^oC mp)

Liquids and vapor pressure

Put a lid on a container filled with a liquid so have closed system.

Find some of the molecules in the liquid phase have enough KE to escape from the surface of the liquid and form a vapor phase.

At the same time some of the gas molecules in the vapor phase fall back into the liquid.

               _evaporation

Liquid                          gas

               ^condensation

"At some point in time..."

At some point in time the

Say we have reached a state of dynamic equilibrium.

Pressure exerted by the vapor (gas molecules) above the liquid is called the equilibrium _________________

"The value of the vapor..."

The value of the vapor pressure depends on

Slide 72

"Normal b pt:"

Normal b pt: temp at which the v.p. of the liquid =

Boiling pt depends on strength of intermolecular forces.

"Which will have the greater..."

Which will have the greater vapor pressure at 5^oC? The higher b pt?

CH₃OCH₃ or CH₃CH₂OH

CH₄ or CCl₄

I₂ or Cl₂

Liquid state con’t

Compressibility: increased pressure essentially no effect on liquids and solids--brake fluid

Viscosity: resistance to flow; stronger intermolecular forces, greater viscosity; viscosity decreases with increase in temp.

Liquid state

Surface tension: measure of attractive forces at surface of liquid--leads to sperical shape of drops of liquid

Surfactant (soaps and detergents): decrease surface tension--grease removal

The solid state

Properties: virtually incompressible

Melting point: temp at which change into liquid--depends on strength of intermolecular forces

Types of crystalline solids

Crystalline solids: regular repeating order in 3D structure

Types of crystalline solids

1. Ionic solids:

"2."

2. Covalent (network )solids:

3. Molecular solids:

"4."

4. Metallic solids:


	Instructor: Upali Siriwardane (Ph.D., Ohio State University)
	CTH 311, Tele: 257-4941, e-mail: upali@chem.latech.edu
	Office hours: 10:00 to 12:00 Tu & Th ; 8:00-9:00 and 11:00-12:00 M,W,& F


	Tests will be given in regular class periods from 9:30-10:45 a.m. on the following days:
	September 22, 2004 (Test 1): Chapters 1 & 2
	October 8, 2004(Test 2): Chapters 3, & 4
	October 20, 2004 (Test 3): Chapter 5 & 6
	November 3, 2004 (Test 4): Chapter 7 & 8
	November 15, 2004 (Test 5): Chapter 9 & 10
	November 17, 2004 MAKE-UP: Comprehensive test (Covers all chapters
	Grading:
	[( Test 1 + Test 2 + Test3 + Test4 + Test5)] x.70 + [ Homework + quiz average] x 0.30 = Final Average
	5


	Describe the behavior of gases : Boyle's law, Charles's law, combined gas law, Avogadro's law, the ideal gas law, and Dalton's law.
	2. Use gas law equations to calculate conditions and changes in conditions of gases.
	3. Describe the major points of the kinetic molecular theory of gases.
	4. Explain the relationship between the kinetic molecular theory and the physical properties of macroscopic quantities of gases.
	5. Describe properties of the liquid state.
	6. Describe the processes of melting, boiling, evaporation, and condensation.
	7. Describe the dipolar attractions known collectively as London dispersion (van der Waals) forces.
	8. Describe hydrogen bonding and its relationship to boiling and melting
	temperatures.
	9. Relate the properties of the various classes of solids (ionic, covalent,
	molecular, and metallic) to the structure of these solids.


	By changing the temperature (and pressure) all matter can exist as a solid, as a liquid and as a gas.
	There are forces of attraction (which we learn about later) btn cmpds that determine what physical state (gas, liquid, solid) we find the cmpd in at a given temperature.


	Temperature gives molecules kinetic energy. ______ the temp the ________ the kinetic energy.
	If the strength of attractive forces btn molecules is much larger than the kinetic energy due to temp the cmpd will be a ________
	If the molecules’ kinetic energy due to temp is much greater than the attractive forces btn molecules the cmpd will be a _______
	If the attractive forces and the energy due to temp are similar the cmpd will be a _______


	4. In general for the same substance density of a solid > density of a liquid > density of a gas
	For water density_liquid > density_solid (ice floats)
	See table 6.1


	We are going to describe a gas in terms of the pressure (P) it exerts, the volume (V) it occupies and its temperature (T).
	Pressure is a
	We live at the bottom of a sea of gas molecules which are constantly hitting us and exerting pressure on us.


	The downward force on any surface area (say 1 in²)due to “air” is equal to the mass of the column of air above the area and is 14.7psi (lb/in²).
	We measure the pressure of the atmosphere with a


	P_air = P_Hg in the barometer tube. The downward pressure of the mercury in the column is balanced by the outside atmospheric pressure pressing down on the mercury in the dish.
	We define one atmosphere as the atmospheric pressure which


	1 atm =


	(1 torr = 1 mm Hg)
	Express 528 mm Hg in atm
	Express 2.86 atm in mm Hg and torr.


	4 easily measured macroscopic properties: V, T, P, n (# moles)

	Now we want to develop a mathematical relationship btn P,V,T and the no. of moles (n) of a gas.


	Boyle (1660) did some experiments that showed as the pressure applied to a gas increases, the volume occupied by the gas decreases as long as the temperature and amt of gas is held constant.


	or P µ 1/V and V µ 1/P
	PV = k₁ where k₁ is a proportionality constant that is



	P_iV_i = k₁ and P_fV_f =k₁ so
	P_iV_i = P_fV_f at the same temp and no.moles of gas


	Gases follow Boyle’s law best (PV=k) at
	.

	complete P_i(atm) P_f(atm) V_i(L) V_f(L)
	1.0 0.50 ? 0.30
	1.0 2.0 0.75 ?
	What happens to the volume if you triple the pressure at constant temp and no. moles?


	Charles, a hot air balloonist, (1800’s) investigated how V and T (temperature in K) were related.
	He found that as the temperature of the gas increased, the volume occupied by the gas also increased as long as the pressure and amt of the gas were held constant.


	or V µ T and V = k₂T where k₂ is a proportionality constant that depends on the



	Remember to convert from ^oC to K


	V = k₂T
	V/T = k₂
		k₂ = proportionality constant
		independent of identity of gas
		requires constant P and n
	V_i/T_i = k₂ and V_f/T_f = k₂ so
	V_i/T_i = V_f/T_f
		excellent approximation at


	What happens to the volume when the temp in Kelvin is tripled at constant P and n?


	Avogadro found that the volume of a gas increased as the amt of the gas increased when the pressure and temp were held constant. (balloon)
	V µ n or V = k₃n direct relationship


	Equal volumes of gases under the same conditions of temp and pressure contain equal nos. of particles.

	Equal moles of all gases under the same conditions of temp and pressure have the same volume.


	An ideal gas obeys the gas laws we have developed. A real gas may deviate somewhat from these laws. But under conditions of _____________________, these laws are obeyed. The reason for this will be discussed later.


	STP (standard temp and pressure)


	It is found that 1 mol of a gas occupies a volume of


	Substituting the molar volume at STP in PV=nRT


	V of one mole of gas at STP = 22.4 L
	Same V regardless of identity of gas!
	but
		22.4 L of N₂

		22.4 L of CH₄(g)


	d =
	At STP
	1 mol of H₂ has a mass of 2.0 g so d_H2 =
	1 mol of O₂ has a mass of 32.0 g so d_O2 =
	1 mol of CO has a mass of 28.0 g so d_CO =


	The temp has to be in
	In the comparative laws (Boyle’s, Charles’, etc) pressure and volume just have to be in the same units. n has to be in moles
	In the ideal gas law the units are as specified before.


	A sample of nitrogen gas kept in a container of volume 2.3L and at a temp of 32^oC exerts a pressure of 4.7 atm. Calc the no. of moles and the mass of gas present.


	A balloon has a volume of 43.0L at 20^oC. What is its volume at -5^oC?

	A syringe has a volume of 10.0mL at 14.7psi. If the tip is blocked so that air can’t escape, what pressure is required to decrease the volume to 2.00mL?

	If 20.0g of N₂gas has a volume of 4.00L and a pressure of 6.00atm, what is its temp?


	Which sample contains more molecules: 2.0L of CO₂ at 300K and 500 mm Hg or 1.5L of N₂ at 57^oC and 760 mm Hg? Which sample weighs more?

	An aerosol can has an internal pressure of 3.75atm at 25^oC. What temp is required to raise the pressure to 16.6atm?


	A compressed-air tank carried by scuba divers has a volume of 8.0L and a pressure of 140 atm at 20^oC. What is the volume of air in the tank at 0^oC and 1.00atm pressure (STP)?
	Cyclopropane. C₃H₆, is used as a general anesthetic. If a sample of cyclopropane is stored in a 2.00 L container at 10.0 atm and 25.0^oC is transferred to a 5.00 L container at 5.00 atm, what is its resulting temp?


	What is the effect on a gas if you simultaneously:
	a) halve its pressure and double its Kelvin temp
	b) double its pressure and double its Kelvin tempereature.