Question

Which of the following reactions is NOT correct according to the law of conservation of mass?

Options

• \[\ce{2Mg_{(s)} + O2_{(g)} -> 2MgO_{(s)}}\]

• \[\ce{C3H8_{(g)} + O2_{(g)} -> CO2_{(g)} + H2O_{(g)}}\]

• \[\ce{P4_{(s)} + 5O2_{(g)} -> P4O10_{(s)}}\]

• \[\ce{CH4_{(g)} + 2O2_{(g)} -> CO2_{(g)} + 2H2O_{(g)}}\]

Answer 1

\[\ce{C3H8_{(g)} + O2_{(g)} -> CO2_{(g)} + H2O_{(g)}}\]

Explanation:

According to the law of mass conservation,

Total mass of reactants = Total mass of products

\[\ce{\underset{44 g}{C3H8_{(g)}} + \underset{32 g}{O2_{(g)}} -> \underset{44 g}{CO2_{(g)}} + \underset{18 g}{H2O_{(g)}}}\]

The law of conservation of mass is broken here.

i.e., Mass of reactants ≠ Mass of products