Question

1. Hydrogen and oxygen react chemically to form water. How much water would form if 19.2 grams of hydrogen reacted with 40.1 grams of oxygen? (H2 + O2 → H2O) 

Answer 1

Balanced reaction:

2H₂ + O₂ → 2H₂O

M(H₂) = 2 g/mol

M(O₂) = 32 g/mol

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

n(H₂) $= \frac{19.2}{2} = 9.6 \;mol$

n(O₂) $= \frac{40.1}{32} = 1.25 \;mol$

Proportion from the reaction:

H₂: O₂ = 2:1

Proportion from the reactants masses:

H₂: O₂ = 9.6:1.25

O₂ is the limiting reactant that will completely react.

n(H₂O) = 2n(O₂) $= 2\times1.25 = 2.5\; mol$

M(H₂O) = 18 g/mol

m(H₂O) $= n\times M = 2.5\; mol\times 18\;g/mol = 45\; g$

Answer: 45 g