Question

$N_2\left(g\right)+3H_2\left(g\right)\to 2{NH}_3\left(g\right)+92$ kJ

According to the equation above, what mass of nitrogen gas is required to produce $68$ g of ammonia?

• A. 112 g
• B. 56 g
• C. 44 g
• D. 28 g
• E. 14 g

Answer 1

Answer: (B)

56 g

$N_2\left(g\right)+3H_2\left(g\right)\to 2{NH}_3\left(g\right)+92$ kilojoules

The molar mass of ammonia is 17 g/mol.

68 grams of ammonia corresponds to $\frac{68}{17}=4$ moles.

2 moles of ammonia are obtained from 1 mole of nitrogen.

4 moles of ammonia are obtained from $4\times \frac{1}{2}=2$ moles of nitrogen.

The molar mass of nitrogen is 28 g/mol.

The mass of nitrogen is $2\times 28=56$ grams.

Thus, $56$ g of nitrogen gas is required to produce $68$ g of ammonia.