Question

How many grams of H2 are needed to produce 11.16 g of NH3?

Answer 1

The Stoichiometric equaton for the formation of NH₃ from N₂ and H₂ is

N₂ + 3 H _{2 =} 2 NH₃

Molar mass of H₂ = 2 x1.008= 2.016.g/mol

Molar mass of NH₃ = 14.00 +3x1.008 = 17.024 g/mol

According to the stoichiometric equation

2 mol of NH₃ is produced from 3 mol of H₂

ie 2 x 17.024 g of NH₃ is produced from 3 x 2.016.g of H₂

Therefore

A VERY USEFUL TIP:

The crucial step in solving this (and similar problems) is

2 mol of NH₃ is produced from 3 moles of H₂

You ALWAYS make this statement with the quantity to be found out on the RHS.

In this problem you are required to calculate the amount of H_2.Hence we write the statement with H₂ on the RHS.

USE THIS GENERAL PRINCIPLE IN ALL PROBLEMS INVOLVING ONLY 2 QUANTITES LIKE

Mole- mass ,

Mole- Volume,

Mole- Number of particles

Volume - Number of particles

etc