41. In the reaction H2(g)+Cl2(g)⇌2HCl(g)H2(g)+Cl2(g)⇌2HCl(g), the equilibrium constant KcKc is 100 at a given temperature. What will be the equilibrium constant for the reverse reaction?
a) 1
b) 10
c) 0.01
d) 0.1
Answer: c) 0.01
Explanation:
For the reverse reaction, the equilibrium constant is the reciprocal of the forward reaction’s KcKc. Thus, Kc(reverse)=1100=0.01Kc(reverse)=1001=0.01.
42. For the dissociation reaction of PCl5(g)⇌PCl3(g)+Cl2(g)PCl5(g)⇌PCl3(g)+Cl2(g), increasing the concentration of Cl2Cl2 will:
a) Shift the equilibrium to the right
b) Shift the equilibrium to the left
c) Increase the concentration of PCl5PCl5
d) Both b and c
Answer: d) Both b and c
Explanation:
Increasing the concentration of Cl2Cl2 will shift the equilibrium to the left (towards PCl5PCl5) according to Le Chatelier’s principle, thereby increasing the concentration of PCl5PCl5.
43. Which of the following changes will NOT affect the position of equilibrium in the reaction H2(g)+I2(g)⇌2HI(g)H2(g)+I2(g)⇌2HI(g)?
a) Increasing the pressure
b) Adding more H2H2
c) Decreasing the temperature
d) Adding a catalyst
Answer: d) Adding a catalyst
Explanation:
A catalyst speeds up the forward and reverse reactions equally but does not affect the position of equilibrium or the equilibrium constant.
44. For the reaction N2(g)+3H2(g)⇌2NH3(g)N2(g)+3H2(g)⇌2NH3(g), what will happen if the volume of the container is decreased?
a) The equilibrium will shift to the right.
b) The equilibrium will shift to the left.
c) The equilibrium will remain unchanged.
d) The value of KcKc will increase.
Answer: a) The equilibrium will shift to the right.
Explanation:
Decreasing the volume increases the pressure. Since there are fewer moles of gas on the right side (2 moles of NH3NH3) compared to the left side (4 moles of N2+H2N2+H2), the equilibrium shifts to the side with fewer moles of gas.
45. The dissociation constant (KaKa) of acetic acid is 1.8×10−51.8×10−5. Which of the following is the correct expression for the pH of a 0.1 M solution of acetic acid?
a) pH = 7
b) pH = 1
c) pH = 5
d) pH = 2.9
Answer: d) pH = 2.9
Explanation:
Using the formula for a weak acid, [H+]=Ka⋅[HA][H+]=Ka⋅[HA], we calculate the concentration of H+H+ and then find the pH. For acetic acid, pH≈2.9pH≈2.9.
46. Which of the following is an example of a Lewis acid?
a) OH−OH−
b) NH3NH3
c) BF3BF3
d) H2OH2O
Answer: c) BF3BF3
Explanation:
A Lewis acid is an electron pair acceptor. BF3BF3 lacks a complete octet on the boron atom and can accept electron pairs, making it a Lewis acid.
47. In the equilibrium CO2(g)+H2O(l)⇌H2CO3(aq)CO2(g)+H2O(l)⇌H2CO3(aq), what will be the effect of increasing the pressure?
a) The equilibrium shifts to the left.
b) The equilibrium shifts to the right.
c) The value of KcKc increases.
d) The equilibrium constant decreases.
Answer: b) The equilibrium shifts to the right.
Explanation:
Increasing the pressure will shift the equilibrium to the side with fewer gas molecules. Since there is only one gas molecule on the left and no gas on the right, the equilibrium shifts to the right.
48. For the dissociation of water, H2O(l)⇌H+(aq)+OH−(aq)H2O(l)⇌H+(aq)+OH−(aq), at 298 K, the value of KwKw is 1×10−141×10−14. What is the pH of pure water?
a) 7
b) 14
c) 1
d) 5
Answer: a) 7
Explanation:
For pure water, [H+]=[OH−]=Kw=1×10−7[H+]=[OH−]=Kw=1×10−7. Therefore, the pH is −log[H+]=7−log[H+]=7, which is neutral at 298 K.
49. Which of the following will increase the degree of dissociation of a weak acid in water?
a) Adding a common ion
b) Increasing the concentration of the acid
c) Diluting the solution
d) Adding a strong acid
Answer: c) Diluting the solution
Explanation:
According to Ostwald’s dilution law, the degree of dissociation of a weak acid increases as the solution is diluted.
50. The value of KcKc for the reaction H2(g)+I2(g)⇌2HI(g)H2(g)+I2(g)⇌2HI(g) is 50. What is the equilibrium concentration of HIHI if the concentrations of H2H2 and I2I2 are both 0.1 M?
a) 0.5 M
b) 0.1 M
c) 0.7 M
d) 0.05 M
Answer: a) 0.5 M
Explanation:
Using the expression for KcKc, Kc=[HI]2[H2][I2]Kc=[H2][I2][HI]2, and solving for [HI][HI], the equilibrium concentration of HI is found to be 0.5 M.
51. Which of the following solutions will have a pH greater than 7?
a) NaCl
b) NH44Cl
c) Na22CO33
d) HCl
Answer: c) Na22CO33
Explanation:
Na22CO33 is a salt of a strong base (NaOH) and a weak acid (H22CO33). It undergoes hydrolysis in water to produce OH−− ions, making the solution basic with a pH greater than 7.
52. Which of the following will have the highest solubility in an acidic solution?
a) Mg(OH)22
b) AgCl
c) NaCl
d) CaCO33
Answer: a) Mg(OH)22
Explanation:
Magnesium hydroxide is a sparingly soluble base. In an acidic solution, the H++ ions react with OH−−, increasing the solubility of Mg(OH)22.
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