Which of the following reactions is incorrectly labeled?

a. HCl (aq) + NaOH (aq) = NaCl (aq) + H2O (l) - Precipitation reaction.

b. CH4 (g) + 3 O2 (g) = CO2 (g) + 2 H2O (l) - Combustion reaction.

c. No right choice.

The option a termed as precipitation reaction is incorrectly labelled.

Explanation:

The chemical reactions are classified based on the reactants used and products formed in a reaction. They are decomposition reaction, single displacement reaction, double displacement reaction, acid-base neutralisation reaction, precipitation reaction, combustion reaction, redox reaction and organic reaction.

Among these, the given options are labelled as precipitation and combustion reaction. The one which is labelled as combustion reaction is correct because combustion reactions occur in the presence of oxygen only and the products of combustion reaction should include water, oxygen or carbon and heat.

The other option which is labelled as precipitation reaction is incorrect because precipitation reaction occurs when an ionic substance will come out of a solution due to heating it or stirring it making the solubility of the ionic substance in a solution zero such that it will come out as solid and form a layer at the bottom of the solution.

But in this case all the products are in aqueous state, there is absence of any ionic substance in solid state, so the option which is labelled as precipitation reaction is incorrectly labelled.