Question

Write balanced molecular and net ionic equations for the following reactions, and identify the gas formed in each: (a) solid cadmium sulfide reacts with an aqueous solution of sulfuric acid; (b) solid magnesium carbonate reacts with an aqueous solution of perchloric acid.

Short answer

The balanced net ionic equations for the given reactions are: (a) $Cd{S}_{(s)}+2H_{(aq)}^{+}\to C{d}_{(aq)}^{2+}+H_2{S}_{(g)}$ with hydrogen sulfide (H2S) gas formed. (b) $\text{Double subscripts: use braces to clarify}$ with carbon dioxide (CO2) gas formed.

Step-by-step solution

Write the unbalanced molecular equation

The given reaction can be represented as: $\text{Double subscripts: use braces to clarify}$ products

Identify the products

Cadmium sulfide reacts with sulfuric acid to form cadmium sulfate and hydrogen sulfide gas: $\text{Double subscripts: use braces to clarify}$

Balance the molecular equation

The equation is already balanced: $\text{Double subscripts: use braces to clarify}$

Write the complete ionic equation

As the reaction occurs in aqueous solution, dissociate the strong electrolytes: $\text{Double subscripts: use braces to clarify}$

Write the net ionic equation

Remove spectator ions, which are the same on both sides of the equation: $Cd{S}_{(s)}+2H_{(aq)}^{+}\to C{d}_{(aq)}^{2+}+H_2{S}_{(g)}$ The balanced net ionic equation is: $Cd{S}_{(s)}+2H_{(aq)}^{+}\to C{d}_{(aq)}^{2+}+H_2{S}_{(g)}$ The gas formed is hydrogen sulfide (H2S). (b) Solid magnesium carbonate reacts with an aqueous solution of perchloric acid:

Write the unbalanced molecular equation

The given reaction can be represented as: $\text{Double subscripts: use braces to clarify}$ products

Identify the products

Magnesium carbonate reacts with perchloric acid to form magnesium perchlorate and carbon dioxide gas: $\text{Double subscripts: use braces to clarify}$

Balance the molecular equation

Balance the equation by adding coefficients: $\text{Double subscripts: use braces to clarify}$

Write the complete ionic equation

As the reaction occurs in aqueous solution, dissociate the strong electrolytes: $\text{Double subscripts: use braces to clarify}$

Write the net ionic equation

Remove spectator ions, which are the same on both sides of the equation: $\text{Double subscripts: use braces to clarify}$ The balanced net ionic equation is: $\text{Double subscripts: use braces to clarify}$ The gas formed is carbon dioxide (CO2).