Question

How many molecules of ammonia are produced from 2.75*10^(-4) grams of hydrogen? Express answer numerically as the number of molecules.

Answer 1

N₂ + 3H₂ → 2NH₃

M(H₂) = 2.016 g/mol

$n = \frac{m}{M}$

n(H₂) $= \frac{2.75 \times 10^{-4}}{2.016} = 1.36 \times 10^{-4} \;mol$

According to the reaction equation:

n(NH₃) $= \frac{2}{3}n(H2) = 0.90 \times 10^{-4} \;mol$

A mole of ammonia contains 6.02×10²³ molecules.

Proportion:

1 mol – $6.02 \times 10^{23}$ molecules

$0.90 \times 10^{-4}$ mol – x molecules

$x = \frac{6.02 \times 10^{23} \times 0.90 \times 10^{-4}}{1} = 5.418 \times 10^{19}$

Answer: $5.418 \times 10^{19}$ molecules