Question:
How many grams of NH3 can be produced from 16.0 g of N2 and excess H2?
Solution:
First let's balance the reaction
N2 + H2 ==> NH3
N2 + 3*H2 ==> 2*NH3
So for every N2 we get 2*NH3
Given:
N2 = 16.0 g
From the Periodic Table:
1 mole N = 14.007 g
1 mole H = 1.008 g
How many moles of N do we have?
16.0 g of N2 * (1 mole N / 14.007 g) = 1.14 moles of N
This is the same number of moles for NH3.
NH3 weighs N + 3*H
= 14.007 g + 3*1.008 g = 17.03 g / mole
Multiple to solve:
1.14 moles of NH3 * 17.03 g / mole = 19.42 g
THEREFORE
19.42 g of NH3 can be produced