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

(a) The balanced molecular and net ionic equations for the reaction between solid cadmium sulfide and aqueous sulfuric acid are: CdS (s) + H2SO4 (aq) → CdSO4 (aq) + H2S (g) CdS (s) + 2H⁺ (aq) → Cd²⁺ (aq) + H2S (g) The gas formed in this reaction is hydrogen sulfide (H2S). (b) The balanced molecular and net ionic equations for the reaction between solid magnesium carbonate and aqueous perchloric acid are: MgCO3 (s) + 2HClO4 (aq) → Mg(ClO4)2 (aq) + CO2 (g) + H2O (l) MgCO3 (s) + 2H⁺ (aq) → Mg²⁺ (aq) + CO2 (g) + H2O (l) The gas formed in this reaction is carbon dioxide (CO2).

Step 1: Write the unbalanced equation

The given reaction is between solid cadmium sulfide (CdS) and an aqueous solution of sulfuric acid (H2SO4). Write the unbalanced equation for the reaction: CdS (s) + H2SO4 (aq) → ...

Step 2: Predict the products and balance the equation

The reaction between CdS and H2SO4 will form cadmium sulfate (CdSO4) and hydrogen sulfide gas (H2S). Write the balanced equation for the reaction: CdS (s) + H2SO4 (aq) → CdSO4 (aq) + H2S (g)

Step 3: Write the net ionic equation

First, write the complete ionic equation: CdS (s) + 2H⁺ (aq) + SO₄²⁻ (aq) → Cd²⁺ (aq) + SO₄²⁻ (aq) + H2S (g) Eliminate the spectator ions, in this case, SO₄²⁻ (aq), to get the net ionic equation: CdS (s) + 2H⁺ (aq) → Cd²⁺ (aq) + H2S (g) The gas formed in this reaction is hydrogen sulfide (H2S). (b) Solid magnesium carbonate reacts with an aqueous solution of perchloric acid.

Step 1: Write the unbalanced equation

The given reaction is between solid magnesium carbonate (MgCO3) and an aqueous solution of perchloric acid (HClO4). Write the unbalanced equation for the reaction: MgCO3 (s) + HClO4 (aq) → ...

Step 2: Predict the products and balance the equation

The reaction between MgCO3 and HClO4 will form magnesium perchlorate (Mg(ClO4)2) and carbon dioxide gas (CO2) as well as water (H2O). Write the balanced equation for the reaction: MgCO3 (s) + 2HClO4 (aq) → Mg(ClO4)2 (aq) + CO2 (g) + H2O (l)

Step 3: Write the net ionic equation

First, write the complete ionic equation: MgCO3 (s) + 2H⁺ (aq) + 2ClO₄⁻ (aq) → Mg²⁺ (aq) + 2ClO₄⁻ (aq) + CO2 (g) + H2O (l) Eliminate the spectator ions, in this case, 2ClO₄⁻ (aq), to get the net ionic equation: MgCO3 (s) + 2H⁺ (aq) → Mg²⁺ (aq) + CO2 (g) + H2O (l) The gas formed in this reaction is carbon dioxide (CO2).