Chemistry Question

Question

Silicon nitride, a very hard, high-temperature resistant ceramic used as the material for turbine blades in jet engines is prepared by reacting silicon with nitrogen gas. The balanced chemical reaction is given below:

3 Si_(s) + 2 N_{2 (g)}  ➜  Si₃N_{4 (s)} 

A. What mass of nitrogen gas (molar mass: 28.014 g/mol) reacts with 10.00 g of silicon (molar mass: 28.085 g/mol)?

a.

6.667 g N₂

b.

14.96 g N₂

c.

15.00 g N₂

d.

6.650 g N₂

B. How much Si₃N₄ (molar mass: 140.28 g/mol) is produced by reacting 10.00 g of silicon in excess nitrogen gas?

a.

14.98 g Si₃N₄

b.

16.65 g Si₃N₄

c.

30.00 g Si₃N₄

d.

3.333 g Si₃N₄

C. If the actual amount of Si₃N₄ produced from 10.00 g of silicon is 11.31 g, what is the percent yield of the reaction?

a.

37.70%

b.

342.7%

c.

75.50%

d.

67.93%

Answer 1

3 Si_(s) + 2 N_{2 (g)}  ➜  Si₃N_{4 (s)} ... balanced equation

A. What mass of nitrogen gas (molar mass: 28.014 g/mol) reacts with 10.00 g of silicon (molar mass: 28.085 g/mol)?

10.00 g Si x 1 mol Si / 28.085 g x 2 mol N₂ / 3 mol Si x 28.014 g N₂/mol = 6.650 g N₂ (Ans. d)

B. How much Si₃N₄ (molar mass: 140.28 g/mol) is produced by reacting 10.00 g of silicon in excess nitrogen gas?

10.00 g Si x 1 mol Si / 28.085 g x 1 mol Si₃N₄ / 3 mol Si x 140.28 g Si₃N₄ / mol = 16.65 g Si₃N₄ (Ans. b)

C. If the actual amount of Si₃N₄ produced from 10.00 g of silicon is 11.31 g, what is the percent yield of the reaction?

% yield = actual yield / theoretical yield (x100%) = 11.31 g / 16.65 g (x100%) = 67.93% (Ans. d)