Question

What is the mass in grams of H₂ that can be formed from 39.8 grams of NH₃ in the following reaction?2 NH₃(g) → 3 H₂(g) + N₂(g)

Answer 1

Answer

mass of H2 = 7.1 g

Explanation

Given:

$2NH_{3(g)}\rightarrow3H_{2(g)}+N_{2(g)}$

mass of NH3 = 39.8 g

Required: mass of H2 that will be formed

Solution

Step 1: Use stoichiometry to solve this problem, first calculate the number of moles of NH3

n = m/M where n is the moles, m is the mass and M is the molar mass

n = 39.8g/17,03 g/mol

n = 2.3 mol

Step 2: Use the molar ratio to find the moles of H2

The molar ratio between NH3 and H2 is 2:3

Therefore, moles of H2 = 2.3 x (3/2) = 3.5 mol

Step 3: Convert the moles of H2 to mass in grams

m = n x M

m = 3.5 mol x 2.0156 g/mol

m = 7.1 g