Problem 41 - Chemistry The Central Science

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.

Step-by-Step Solution

Answer

In the reaction between solid cadmium sulfide (CdS) and an aqueous solution of sulfuric acid (H2SO4), the balanced molecular equation is: \(CdS (s) + H2SO4 (aq) \rightarrow CdSO4 (aq) + H2S (g)\). The net ionic equation is: \(CdS (s) + 2H^+ (aq) \rightarrow Cd^{2+} (aq) + H2S (g)\). The gas formed is hydrogen sulfide (H2S). In the reaction between solid magnesium carbonate (MgCO3) and an aqueous solution of perchloric acid (HClO4), the balanced molecular equation is: \(MgCO3 (s) + 2HClO4 (aq) \rightarrow Mg(ClO4)2 (aq) + CO2 (g) + H2O (l)\). The net ionic equation is: \(MgCO3 (s) + 2H^+ (aq) \rightarrow Mg^{2+} (aq) + CO2 (g) + H2O (l)\). The gas formed is carbon dioxide (CO2).

Step 1: (Reaction a: Cadmium sulfide with sulfuric acid)

The reaction between solid cadmium sulfide (CdS) and an aqueous solution of sulfuric acid (H2SO4) can be represented as follows: CdS (s) + H2SO4 (aq) -> ? In this reaction, cadmium sulfide (a solid) reacts with sulfuric acid (an aqueous solution) to produce a cadmium sulfate (CdSO4) and hydrogen sulfide (H2S) gas. The balanced molecular equation for this reaction is: CdS (s) + H2SO4 (aq) -> CdSO4 (aq) + H2S (g) Now, let's determine the net ionic equation by identifying the spectator ions and removing them from the equation. The net ionic equation includes only the aqueous ions that undergo a chemical change. For this reaction, the net ionic equation is: CdS (s) + 2H^+ (aq) + SO4^2- (aq) -> Cd^2+(aq) + SO4^2- (aq) + H2S (g) Removing the common ion (spectator ion) SO4^2- from both sides of the equation, the final net ionic equation becomes: CdS (s) + 2H^+ (aq) -> Cd^2+ (aq) + H2S (g)

Step 2: (Reaction b: Magnesium carbonate with perchloric acid)

The reaction between solid magnesium carbonate (MgCO3) and an aqueous solution of perchloric acid (HClO4) can be represented as follows: MgCO3 (s) + HClO4 (aq) -> ? In this reaction, magnesium carbonate (a solid) reacts with perchloric acid (an aqueous solution) to produce magnesium perchlorate (Mg(ClO4)2) and carbon dioxide (CO2) gas. The balanced molecular equation for this reaction is: MgCO3 (s) + 2HClO4 (aq) -> Mg(ClO4)2 (aq) + CO2 (g) + H2O (l) Now, let's determine the net ionic equation by identifying the spectator ions and removing them from the equation. The net ionic equation includes only the aqueous ions that undergo a chemical change. For this reaction, the net ionic equation is: MgCO3 (s) + 2H^+ (aq) + 2ClO4^- (aq) -> Mg^2+(aq) + 2ClO4^-(aq) + CO2 (g) + H2O (l) Removing the common ion (spectator ion) 2ClO4^- from both sides of the equation, the final net ionic equation becomes: MgCO3 (s) + 2H^+ (aq) -> Mg^2+ (aq) + CO2 (g) + H2O (l) So, in conclusion: a) The gas formed in the reaction between solid cadmium sulfide and an aqueous solution of sulfuric acid is hydrogen sulfide (H2S). b) The gas formed in the reaction between solid magnesium carbonate and an aqueous solution of perchloric acid is carbon dioxide (CO2).