CHEMISTRY 161

Chapter 5

www.chem.hawaii.edu/Bil301/welcome.html

REVISIONBoyle’s Law

Gay-Lussac’s Law

Avogadro’s Law

p ∞ 1/V

n ∞ V

V ∞ T

(1) p ∞ 1/V

p × V = const × n × T

(2) V ∞ T

1. IDEAL GAS EQUATION

(3) n ∞ V

V ∞ 1/p

V ∞ T

V ∞ n

V ∞ T × n / p

p × V = const × n × T

p × V = R × n × T

p × V = n × R × T

ieal gas equation

p × V = n × R × T

[R] = [p] × [V] / [n] / [T]

Pa = N/m2 m3 mol K

[R] = N × m / mol / K

[R] = J / mol / K

R = 8.314 J / mol / K

[R] = J / mol / K

ideal gas constant

p × V = n × R × T

2. MOLAR VOLUME

What is the volume of 1 mol of a gas at

273.15 K (0oC) and 1 atm (101,325 Pa)?

standard temperature and pressure

(STP)

V = 22.4 l

p × V = n × R × T

the molar volume at standard pressure and temperature is independent on the gas type

V = 22.4 l

Vm = 22.4 l

3. STOICHIOMETRY

NaN3(s) → Na(s) + N2(g)

How many liters of nitrogen gas are produced in the decomposition of 60.0 g sodium azide at 80oC and 823 torr?

1. Balancing

2. Mole ratios

3. Convert grams into moles

4. Convert moles into liters

4. DENSITY CALCULATION

p × V = n × R × T

ς = m / V

relate the moles (n) to the mass (m) via the molecular weight (M)

n = m / M m = n × M

V = n × R × T / p

ς = p × M / (R × T)

5. DALTON’S LAW

Dalton

(1801)

pure gases

gas mixtures

(atmospheres)

DALTON’S LAW

the total pressure of a gas mixture, p, is the sum of the

pressures of the individual gases (partial pressures) at a

constant temperature and volume

p = pA + pB + pC + ….

pA × V = nA × R × T pA = nA × R × T / V

pB × V = nB × R × T

p × V = n × R × T

pB = nB × R × T / V

p = pA + pB

p = (nA + nB) × R × T / V

p × V = n × R × T

pA = nA × R × T / V

p × V = (nA + nB) × R × T

pA / p = nA /(nA + nB) = xA

mole fraction

x < 1

pA = xA × p

A gas mixture contains 4.46 moles of neon, 0.74 moles of Ar, and 2.15 moles of xenon. Calculate

the partial pressure of each gas if the total pressure is 2.0 atm.

2 KClO3 → 2 KCl + 3 O2

SUMMARY

p × V = n × R × T

1. ideal gas equation

R = 8.314 J / mol / K

Vm = 22.4 l

2. molar volume

ς = p × M / (R × T)

3. Density of gases

4. Dalton’s Law

p = Σ pii=1

n

Homework

Chapter 5, p. 166-179problems