Question

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20. Ammonia is synthesized industrially by the reaction of nitrogen and hydrogen in the presence of an iron catalyst according to the reaction equation below. What effect would removing the iron catalyst have on this reaction? Fe 3H,(g) + N2(g) 2NH;(g) A) The reaction would shift to the right, producing more ammonia. B) The reaction rate would increase. C) The reaction would shift to the left, and consume ammonia. D) The reaction rate would decrease. E) There would be no effect on the reaction since Fe is not consumed in the reaction. 21. The reaction A + 2B + C D+ 2E is second order in reactant A, first order in B, and 01.8 ( second order in C. What is the rate law equation for this reaction? rate - [A][2B][C} [A][B]/2[C] rate = k[A]°[B][C A) D) rate [A][B][C B) E) rate = rate - [A][B][2C) 22. What is the correct nuclear symbol for the unknown product "X" in the nuclear equation shown below? U-+X+He A) 평Th B) Ra c) "U D) Pu E) Pu 23. Which type of radiation emitted by radioactive nuclei is the slowest moving and least penetrating? A) positron D) None of the choices are correct. E) alpha B) C) beta gamma 24. The isotope Ni decays to Cu by emitting radiation. What type of radiation is emitted? positron D) None of the choices are correct. E) A) alpha B) beta C) gamma 25. A 50-mg sample of iodine-131 was placed in a container 32.4 days ago. If its half-life is 8.1 days, how many milligrams of iodine-131 are now present? A) 47.3 mg B) 3.1 mg C) 3.24 mg D) 0.81 mg E) 6.2 mg

Answer 1

SOLUTION:

(20)

In this reaction, Fe acts as a catalyst. We know that catalyst has no effect in changing equilibrium.

Hence option (A) and (C) are incorrect.

Instead, the catalyst can increase the rate of the reaction and hence helps to reach equilibrium quickly.

When Fe is removed, the rate of the reaction will be decreased.

So the correct option is (D) The reaction rate would decrease.

(21)

A - second order

B - first order

C- second order

Hence the rate law is given by:

rate = K.[A] [B].[92

So the correct option is (A)

(22)

Given reaction:

238UX+ He

Here, the X should be with atomic number (92 - 2) = 90 = Thorium (Th)

And mass number = (238 - 4 ) =234

So the X is  $\small ^{234}_{90}Th$

So the correct option is (A)

(23)

Correct option is (E) None of the choices are correct.

(24)

The reaction will be as follows:

Ni Th + be

That is beta particle is emitted.

So the correct option is (B) Beta

(25)

Mass of iodine-131 left is given by:

(7)*'w=w

32.4/8.1 m = 50 mg

m = 50 mg * (1) *

m = 3.125 mg

So the correct option is (B) 3.1 mg