Which of the following statements is false?

a)

a catalyst alters the mechanism of reaction.

b)

a catalyst increases the rate of the forward reaction, but does not alter the reverse rate.

c)

a catalyst alters the activation energy.

d)

a catalyst may be altered in the reaction, but is always regenerated.

e)

a catalyst increases the rate of reaction, but is not consumed.

B) A catalyst increases the rate of the forward reaction,but does not alter the reverse rate.

Explanation:

A catalyst is a substance that increases the rate of reaction by providing an alternate mechanism which has low activation energy.

Hence options A and C are correct.

A catalyst increases the rate of forward and backward reaction to the same extent so that the equilibrium conditions remains unchanged.

Hence option B is wrong.

It is obvious that catalysis increases the rate of reaction but is not consumed.

It may be altered in the reaction but is always regenerated at the end.

Hence options D and E are correct.

n2(g) + 3h2-> 2nh3(g)   this is the balanced equation

note the mole ratio between n2, h2 and nh3.   it is 1 : 3 : 2   this will be important.

moles n2 present = 28.0 g n2 x 1 mole n2/28 g = 1 mole n2 present

moles h2 present = 25.0 g h2 x 1 mole h2/2 g = 12.5 moles h2 present

based on mole ratio, n2 is limiting in this situation because there is more than enough h2 but not enough n2.

moles nh3 that can be produced = 1 mole n2 x 2 moles nh3/mole n2 = 2 moles nh3 can be produced

grams of nh3 that can be produced = 2 moles nh3 x 17 g/mole = 34 grams of nh3 can be produced

note:   the key to this problem is recognizing that n2 is limiting, and therefore limits how much nh3 can be produced.