化學問題急 +20

化學問題急 +20

2009-06-09 10:52 pm

16. For the exothermic reaction 3H2(g) + N2(g) 2NH3(g) what is the effect of raising the temperature of the reaction vessel?
A) the reaction will shift left to right
B) the reaction will shift right to left
C) there will be no further reaction
D) what happens depends on the temperature

17. For the exothermic reaction 3H2(g) + N2(g) 2NH3(g) what is the effect of doubling the volume of the reaction vessel?
A) the reaction will shift left to right
B) the reaction will shift right to left
C) there will be no further reaction
D) what happens depends on the temperature

18. For the exothermic reaction 3H2(g) + N2(g) 2NH3(g) which of the following changes could be carried out in such a way as to not cause the reaction to shift either to the left or to the right?
A) adding H2 and removing NH3
B) adding H2 and lowering the temperature
C) adding H2 and raising the temperature
D) adding H2 and decreasing the volume

19. For the exothermic reaction 3H2(g) + N2(g) 2NH3(g) which of the following changes could be carried out in such a way as to not cause the reaction to shift either to the left or to the right?
A) raising the temperature and removing NH3
B) lowering the temperature and adding NH3
C) both (a) and (b)
D) neither (a) nor (b)

20. When considering the effect of a catalyst on a system to which LeChatelier's Principle can be applied, which of the following is true?
A) addition of a catalyst has absolutely no effect on the reaction
B) addition of a catalyst speeds up the forward reaction
C) addition of a catalyst speeds up the reverse reaction
D) addition of a catalyst speeds up both the forward and reverse reaction by the same amount

回答 (1)

Uncle Michael

2009-06-10 4:16 am

✔ 最佳答案

16.
The answer is B.

The equilibrium position (NOT the reation) will shift to the left because the backwards reaction is endothermic. According to Le Chatelier's principle, raising the temperature would favour the endothermic reaction.

17.
The answer is B.

Refer to the equation. There are 4 moles of gaseous molecules on the left and 2 moles on the right.

When the volume is doubled, pressure decreases. According to Le Chatelier's principle, the equilibrium positive (NOT the reaction) will shift to the left in order to increase the number of gaseous molecules.

18.
The answer is C.

A : Both adding H2 and removing NH3 would shift the equilibrium position to the right.

B : Both adding H2 and lowering the temperature would shift the equilibrium position to the right.

C : Adding H2 would shift the equilibrium position to the right, but raising the temperature would shift the equilibrium to the left. The two effects may cancel each other.

D : Both adding H2 and decreasing the volume (increasing the pressure) would shift the equilibrium position to the right.

19.
The answer is C.

Raising the temperature would shift the equilibrium position to the left, but removing NH3 would shift the equilibrium to the right. The two effects can cancel each other.

Lowering the temperature would shift the equilibrium position to the right, but adding NH3 would shift the equilibrium to the left. The two effects can cancel each other.

20.
The answer is D.

Catalyst can speed up both the forward and backward reaction to the same extent. Therefore, catalyst has no effect on equilibrium position.
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化學問題 急 +20

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