1.For the reaction H2(g) + I2(g) 2HI(g), Kc = 50.2 at 445ºC. If [H2] = [I2] = [H
ID: 881130 • Letter: 1
Question
1.For the reaction H2(g) + I2(g) 2HI(g), Kc = 50.2 at 445ºC.
If [H2] = [I2] = [HI] = 1.75 × 10–3 M at 445ºC.
Which of the following is true based on the above?
A) Qc > Kc, the reaction proceeds from left to right to reach equilibrium
B) Qc > Kc, the reaction proceeds from right to left to reach equilibrium
C) Qc < Kc, the reaction proceeds from left to right to reach equilibrium
D) Qc < Kc, the reaction proceeds from right to left to reach equilibrium
E) Qc = Kc, the reaction is currently at equilibrium
2.For the following reaction at equilibrium, which change will cause the equilibrium to shift to the left?
2NOBr(g) 2NO(g) + Br2(g), Hºrxn = 30 kJ/mol
A) Increase the container volume.
B) Remove some NO.
C) Remove some Br2 .
D) Add more NOBr.
E) Decrease the temperature.
3.Concerning the following reaction at equilibrium:
3Fe(s) + 4H2O(g) Fe3O4(s) + 4H2(g), increasing the volume of the container would:
A) Shift the equilibrium to the right
B) Shift the equilibrium to the left
C) Increase the value of the equilibrium constant, K
D) Decrease the value of the equilibrium constant, K
E) No change
4.In the reaction: CH3COOH(aq) + NH2– (aq) CH3COO– (aq) + NH3(aq), the conjugate acid-base pairs are:
A) pair 1: CH3COOH and CH3COO– ; pair 2: NH2– and NH3
B) pair 1: CH3COOH and NH3; pair 2: NH2– and CH3COO–
C) pair 1: CH3COOH and NH2– ; pair 2: NH3 and CH3OO–
D) pair 1: CH3COOH and CH3COO– ; pair 2: NH4+ and NH3
E) pair 1: CH3COOH and CH3COO– ; pair 2: NH2– and NH3+
5.Which one of these net ionic equations represents the reaction of a strong acid with a strong base?
A) H+(aq) + OH–(aq) H2O(aq)
B) H+(aq) + CH3NH2(aq) CH3NH3+(aq)
C) OH–(aq) + HCN(aq) H2O(aq) + CN–(aq)
D) HCN(aq) + CH3NH2(aq) CH3NH3+(aq) + CN–(aq)
6.Predict the direction in which the equilibrium will lie for the reaction
H3PO4(aq) + HSO4–(aq) H2PO4–(aq) + H2SO4(aq).
Ka1(H3PO4) = 7.5 × 10–3; Ka(H2SO4) = very large
A) to the right
B) to the left
C) in the middle
7.Which one of these salts will form a basic solution upon dissolving in water?
A) NaI
B) NaF
C) NH4NO3
D) LiBr
E) Cr(NO3)3
8.The pH of coffee is approximately 5.0. How many times greater is the [H3O+] in coffee than in tap water having a pH of 8.0?
A) 0.62
B) 1.6
C) 30
D) 1,000
E) 1.0 × 104
9.Which one of these salts will form a neutral solution on dissolving in water?
A) NaCl
B) KNO2
C) NaCN
D) NH4NO3
E) FeCl3
10.When the following reaction is at equilibrium, which of these relationships is always true?
2NOCl(g) 2NO(g) + Cl2(g)
A) [NO] [Cl2] = [NOCl]
B) [NO]2 [Cl2] = [NOCl]2
C) [NOCl] = [NO]
D) 2[NO] = [Cl2]
E) [NO]2 [Cl2] = Kc[NOCl]2
11.A 0.10 M NH3 solution is 1.3% ionized. Calculate the H+ ion concentration.
NH3 + H2O NH4+ + OH–
A) 1.3 × 10–3 M
B) 7.7 × 10–2 M
C) 7.7 × 10–12 M
D) 0.13 M
E) 0.10 M
Explanation / Answer
No.1 For the reaction H2(g) + I2(g) <==> 2HI(g), Kc = 50.2 at 445ºC.
If [H2] = [I2] = [HI] = 1.75 × 10–3 M at 445ºC.
Qc= [HI]^2/[H2][I2]= 1
Ans: C) Qc < Kc, the reaction proceeds from left to right to reach equilibrium
No 2.For the following reaction at equilibrium
2NOBr(g) <==> 2NO(g) + Br2(g), Hºrxn = 30 kJ/mol
In an endothermic reactions, decrease in temperature decreases the K value. The above reaction is an endothermic reaction.
Ans: E) Decrease the temperature will cause the equilibrium to shift to the left.
No.3 Concerning the following reaction at equilibrium:
3Fe(s) + 4H2O(g) <==> Fe3O4(s) + 4H2(g), increasing the volume of the container would:
Ans: E) No change
No. 4 In the reaction: CH3COOH(aq) + NH2– (aq) CH3COO– (aq) + NH3(aq), the conjugate acid-base pairs are:
Ans: B) pair 1: CH3COOH and NH3; pair 2: NH2– and CH3COO–
No.5 The following net ionic equations represents the reaction of a strong acid with a strong base
Ans: A) H+(aq) + OH–(aq) <==> H2O(aq)
No.6 The equilibrium for the following reaction will lie:
H3PO4(aq) + HSO4–(aq) <==> H2PO4–(aq) + H2SO4(aq).
Ka1(H3PO4) = 7.5 × 10–3; Ka(H2SO4) = very large
Ans: B) to the left
No.7 Ans: B) NaF
NaF + H2O(l) <==> NaOH(aq) + HF(aq) NaOH is a very strong base and HF is weaker comared to HBr or HI.
No.8 pH= -log [H+] So, [H+] is coffee and tap water are 10^-5 and 10-8 respectively.
Thus, Ans: D) 1,000
No.9 A) NaCl
NaCl + H2O(l) <==> NaOH(aq) + HCl(aq)
No.10 For the reaction 2NOCl(g) <==> 2NO(g) + Cl2(g) at equilibrium : Kc should be equal to Qc. Qc= [NO]^2*[Cl2]/[NOCl]^2
Ans: E) [NO]2 [Cl2] = Kc[NOCl]2
No.11 A 0.10 M NH3 solution is 1.3% ionized : NH3 + H2O(l) <==> NH4+(aq) + OH–(aq)
The H+ ion concentration is: 0.013*0.1 = 0.0013 M
Ans: A) 1.3 × 10–3 M
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