Chemistry 202/212
Worksheet 10
Winter 2005
February 3
Oregon State University
A(g) ↔ 2 B(g)
1. The following data are for the system:
Time (s)
PA (atm)
PB (atm
0
1.00
0.00
20
0.83
0.34
40
0.72
0.56
60
0.65
0.70
80
0.62
0.76
100
0.62
0.76
(a) How long does it take the system to reach equilibrium?
(b) How does the rate of the forward reaction compare with the rate of the reverse
reaction after 30 s? after 90 s?
3 A(g) + 2 B(g) ↔ C(g)
2. Complete the table below for the reaction:
Time(s)
PA (atm)
PB (atm)
PC (atm)
0
2.450
1.500
0.000
10
2.00
20
30
40
1.100
50
60
0.950
0.750
0.275
0.500
3. Write equilibrium constant (K) expressions for the following reactions:
(a) I2(g) + 5 F2(g) ↔ 2 IF5(g)
(b) CO(g) + 2 H2(g) ↔ CH3OH(l)
(c) 2 H2S(g) + 3 O2(g) ↔ 2 H2O(l) + 2 SO2(g)
(d) SnO2(s) + 2 H2(g) ↔ Sn(s) + 2 H2O(l)
4. Given the following data at a certain temperature,
2 N2(g) + O2(g) ↔ 2 N2O(g)
N2O4(g) ↔ 2 NO2(g)
½ N2(g) + O2(g) ↔ NO2(g)
K = 1.2∙10-35
K = 4.6∙10-3
K = 4.1∙10-9
calculate K for the reaction between one mole of dinitrogen oxide gas and oxygen gas to
give dinitrogen tetroxide gas.
5. The reversible reaction between hydrogen chloride gas and one mole of oxygen gas
produces steam and chloride gas:
4 HCl(g) + O2(g) ↔ 2 Cl2(g) + 2 H2O(g)
K = 0.79
Predict the direction in which the system will move to reach equilibrium if one starts with
(a) PH2O = PHCl = PO2 = 0.20 atm
(b) PHCl = 0.30 atm, PH2O = 0.35 atm, PCl2 = 0.2 atm, PO2 = 0.15 atm
6. Solid ammonium carbamate, NH4CO2NH2, decomposes at 25ºC to ammonia and
carbon dioxide according to the following reaction and K value.
NH4CO2NH2(s) ↔ 2 NH3(g) + CO2(g)
K = 2.3∙10-4
In a sealed 10.0 L flask, 7.50 g of NH4CO2NH2(s) is allowed to decompose at 25ºC.
(a) What is the total pressure in the flask when equilibrium is established?
(b) What percentage of NH4CO2NH2(s) decomposed?
(c) Did this reaction take place relatively quickly or slowly?
7. Consider the system
SO3(g) ↔ SO2(g) + ½ O2(g)
∆H = 98.9 kJ
(a) Predict whether the forward or reverse reaction will occur when the equilibrium is
disturbed by
i. adding oxygen gas
ii. decreasing the pressure of the system
iii. adding argon gas
iv. removing SO2(g)
v. decreasing the temperature
(b) Which of the above factors will increase the value of K? Which will decrease it?
8. For each of the following reactions, indicate the Brønsted-Lowry acids and bases.
What are the conjugate acid/base pairs?
(a) H3O+(aq) + CN-(aq) ↔ HCN(aq) + H2O
(b) HNO2(aq) + OH-(aq) ↔ NO2-(aq) + H20
(c) HCHO2(aq) + H2O ↔ CHO2-(aq) + H3O+(aq)
9. Find the pH and pOH of solutions with the following [H+]. Classify each as acidic or
basic.
(a) 6.0 M
(b) 0.33 M
(c) 4.6∙10-8 M
(d) 2.3∙10-14 M
10. Calculate [H+] and [OH-] in solutions with the following pH.
(a) 4.0
(b) 8.52
(c) 0.00
(d) 12.60
11. What is the pH of a solution obtained by adding 13.0 g of NaOH to 795 mL of a
0.200 M solution of Sr(OH)2? Assume no volume change after NaOH is added.