Question

Nitrogen gas and hydrogen gas react to produce ammonia according to the following equation.

N2 + 3H2 → 2NH3

The atomic mass of nitrogen is 14 g/mol. The atomic mass of hydrogen is 1 g/mol. When the reaction produces 68 grams of ammonia, how many grams of nitrogen were present initially?

A 112
B 4
C 56
D 12

Answer 1

C

Step-by-step explanation:

First we have to find the molar mass of NH3 which we can do by adding the atomic masses of all the constituents. 14+3(1) = 17g/mol. Then we convert the grams of ammonia to moles. 68/17=4 moles of ammonia produced. According to the equation, one mole of nitrogen gas corresponds to two moles of ammonia, so for our 4 moles of ammonia, 2 moles of nitrogen gas were there originally. Then we convert that figure into grams using the molar mass of nitrogen gas. 2(14) = 28g/mol and 28*2=56 grams of nitrogen gas.