please i just uploaded the hw, i need someone good in chem, so he can help me with thatCHEMISTRY 401
COSUMNES RIVER COLLEGE
DUE DATE: Tuesday, Sept 29, 2020
CHAPTER 15 HOMEWORK
Direction: For exercises that require problem solving, you need to show the calculation set up leading to the
answer in order to receive credit. Make sure your answers contain the correct units.
1. Write an equilibrium constant expression for each chemical reaction:
Write Kc expression for A, B, C
A. CH4(g) + H2O(g)
B. NiO(s) + CO(g)
CO(g) + 3 H2(g)
Ni(s) + CO2(g)
C. C6H12O6(s) + 6 O2(g)
6 CO2(g) + 6 H2O(l)
Write Kp expression for D, E
D. CO2(g) + C(s)
E. 2 KClO3(s)
2 KCl(s) + 3 O2(g)
2. A chemist trying to synthesize a particular compound attempts two different synthesis reactions that yield the
reaction 1: A + B
K1 = 23.3
reaction 2: C + D
K2 = 2.2 x 104
K1 and K2 are the equilibrium constants for the reactions measured at room temperature (RT). However, upon
carrying out both reactions at RT under the same conditions for 15 minutes, the chemist finds that the reaction
with the smaller equilibrium constant produces more of the desired product. Explain how this might be possible.
3. Consider the following reaction
Kp = 2.2 x 106 at 298 K
CO2(g) + CF4(g)
Calculate Kp for each of the following reaction and predict whether reactants or products will be favored at
equilibrium. Show work set up and set your answer in correct sig figs.
1 CO2(g) + 1 CF4(g)
Answer: Kp = 1.5 x 103
b) 6 COF2(g)
3 CO2(g) + 3 CF4(g)
Answer: Kp = 1.1 x 1019
c) 2 CO2(g) + 2 CF4(g)
Answer: Kp = 2.1 x 10‒13
4. Consider the following reactions and their equilibrium constants:
1 B(g) + C(g)
B(g) + 2 C(g)
K1 = 0.0334
K2 = 2.35
Predict the equilibrium constant for the reaction 2 A(s)
Answer: Knet = 4.75 x 10‒4
5. Calculate Kc for each reaction below. Show work set up and set your answer in correct sig figs.
a) CO(g) + 2 H2(g)
Kp = 2.26 x 104
(at 298 K)
Answer: Kc = 1.35 x 107
b) CH4(g) + H2O(g)
CO(g) + 3 H2(g)
Kp = 7.7 x 1024
(at 298 K)
Answer: Kc = 1.3 x 1022
6. Calculate Kp for each reaction below. Show work set up and set your answer in correct sig figs.
a) N2(g) + 3 H2(g)
Kc = 3.7 x 108
(at 298 K)
Answer: Kp = 6.2 x 105
b) N2(g) + O2(g)
Kc = 4.10 x 10‒31
(at 298 K)
Answer: Kp = Kc = 4.10 x 10‒31
7. Consider the reaction: 2 NO(g) + Br2(g)
Kp = 28.4
(at 298 K)
In a reaction mixture at equilibrium, the partial pressure of NO is 108 torr and and that of Br2 is 126 torr. What
is the partial pressure of NOBr, in torr, in this mixture ? [Hint: All partial pressures must be converted to atm
before using in a Kp expression. Once the answer is obtained in atm, convert it back to torr (or mmHg).]
Answer: PNOBr = 234 torr
8. A vessel filled with gas A to an initial pressure of 1003 mmHg is incubated at a constant temperature until the
decomposition reaction with gas A reaches equilibrium: A(g)
2 B(g). At equilibrium, the partial pressure
of A is 1.90 x 10 mmHg. Calculate Kp.
Answer: Kp = 18.3
9. A reaction mixture is placed in a 3.67-L flask kept at 42 C and consists initially of 0.763 g H2 and 96.9 g I2. At
equilibrium, the flask contains 90.4 g HI. Calculate the equilibrium constant (Kc) for the reaction at this
H2(g) + I2(g)
Answer: Kc = 764
10. The reaction NH4HS(s)
NH3(g) + H2S(g) has a Kc = 8.5 x 10‒3 at 55 C. A reaction vessel contains a
mixture of gaseous NH3 and H2S each at 0.166 M and some solid NH4HS. Is the reaction mixture at
equilibrium ? If not, in what direction will the reaction proceed ? Will more solid NH 4HS form or will some
of the existing solid decompose as equilibrium is reached ?
11. The acetic acid (HC2H3O2) dissociates weakly in aqueous solution as follows:
HC2H3O2(aq) + H2O(l)
H3O+(aq) + C2H3O2‒(aq)
Kc = 1.8 x 10‒5 at 25 C
If a solution initially contains 0.210 M HC2H3O2, what are the equilibrium concentrations of hydronium ion
(H3O+), acetate ion (C2H3O2‒), and acetic acid at 25 C ?
Answer: [H3O+] = [C2H3O2‒] = 1.9 x 10‒3 M; [HC2H3O2] = 0.208 M
12. A sample of CaCO3(s) is introduced into a sealed container of volume 0.654 L and heated to 1000 K until
equilibrium is reached. Heating accelerates the decomposition reaction of CaCO 3 as follows:
CaO(s) + CO2(g)
Kp = 3.9 x 10‒2 (at 1000 K)
Calculate the mass of CaO(s), in gram, and the pressure of CO2(g), in mmHg, that are present at equilibrium.
[Hint: Write the Kp equilibrium expression to find the partial pressure of CO2 at equilibrium. Then use the
ideal gas law to calculate the mol of CO2, which leads to mol CaO and mass of CaO.]
Answer: PCO2 = 3.9 x 10 2 atm; 0.017 g CaO
13. Sulfurous acid (H2SO3) is a weak acid that dissociates partially in aqueous solution:
H2SO3(aq) + H2O(l)
HSO3‒(aq) + H3O+(aq)
At 25 C, H2SO3 has an equilibrium constant of 1.2 x 10‒2. Calculate the equilibrium concentration of H3O+ in
a solution of H2SO3 with an initial concentration of 0.15 M.
Answer: [H3O+] = 0.037 M
14. The reaction CO2(g) + C(s)
2 CO(g) has Kp = 5.78 at 1200 K
4.45 g of CO2(g) is introduced into a 10.0 L container and heated to 1200 K in the presence of 2.00 g of carbon
A. Calculate the total pressure, in atm, of the system at equilibrium. [Hint: Use ideal gas law to determine
initial pressure of CO2(g) in atm. Then set up an ICE table to calculate the equilibrium pressures of CO2
and CO. Note that all pressures must be in atm to be used in Kp expression.]
B. Calculate the mass, in gram, of carbon graphite remaining at equilibrium.
Answer: PT = 1.68 atm; 1.17 g C
15. Consider this reaction at equilibrium:
C(s) + H2O(g)
CO(g) + H2(g)
The reaction is carried out in a closed vessel. Predict whether the reaction will shift left, shift right, or remain
unchanged after each disturbance.
Effect on reaction equilibrium
a) More solid C is added to the reaction mixture.
b) CO is added to the reaction mixture.
c) H2 is removed from the reaction mixture.
d) Gaseous H2O is cooled and condensed to liquid.
e) Volume of the reaction mixture is decreased
(which has same effect as raising the pressure of the system.)
16. For the exothermic reaction C6H12O6(s) + 6 O2(g)
6 CO2(g) + 6 H2O(g)
Predict the following actions on the equilibrium of the reaction. For questions (a) and (b), indicate whether the
equilibrium will shift right, shift left, or remain unchanged. For questions (c) and (d), indicate whether K will
increase or decrease.
Effect on reaction equilibrium
a) Increasing the reaction temperature.
b) Decreasing the reaction temperature.
Effect on equilibrium constant, K
c) Increasing the reaction temperature.
d) Decreasing the reaction temperature.
17. For the endothermic reaction C2H4(g) + I2(g)
If you were trying to maximize the amount of C2H4I2 produced, which of the following tactics might you try ?
Assume that the reaction mixture reaches the equilibrium. Circle all applicable tactics.
a) decreasing the reaction volume.
b) removing I2 from the reaction mixture.
c) raising the reaction temperature.
d) adding C2H4 to the reaction mixture.
e) removing C2H4I2 from the reaction mixture.
18. A sample of SO3 is introduced into an evacuated sealed container and heated to 600 K. The following
equilibrium is established:
2 SO2(g) + O2(g)
At equilibrium, the total pressure in the system is 3.0 atm and the mole fraction of O2 is 0.12. Find Kp.
[Hint: Partial pressure of gas A (PA) = mole fraction of gas A (XA) x Total pressure (PT). Set up ICE table to
find equilibrium pressures of the gases.]
Answer: Kp = 0.051
19. A chemist studying the production of nitrogen monoxide (NO) in the atmosphere adds 0.500 atm of N2, 0.500
atm of O2, and 0.750 atm of NO to a sealed container at 2500 C:
N2(g) + O2(g)
Kp = 8.44 x 10‒3 at 2500 C
a) In which direction will the reaction proceeds to reach equilibrium ?
b) Calculate the equilibrium pressures, in atm, of all three gases.
Answer: PN2 = PO2 = 0.837 atm; PNO = 0.076 atm
20. A container holds an equilibrium mixture of N2O4(g) at 0.28 atm and NO2(g) at 1.1 atm at 350 K:
A. The volume of the container is doubled at constant temperature. What direction will the equilibrium shift ?
B. Calculate the equilibrium pressures of the two gases when the system reaches the new equilibrium.
(You will need to use the quadratic formula to solve this problem.)
Answer: PN2O4 = 0.095 atm; PNO2 = 0.64 atm
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