Which of the following is the correct net ionic equation for the reaction of solid calcium (Ca) with hydrochloric acid (HCl)?

• A. Ca(s) + 2H^+(aq) → Ca^{2+}(aq) + H_2(g)
• B. Ca(s) + 2Cl^-(aq) → CaCl_2(aq)
• C. Ca^{2+}(aq) + 2Cl^-(aq) → CaCl_2(aq)
• D. Ca(s) + 2HCl(aq) → CaH_2(aq) + 2Cl^-(aq)

Answer: (A)

Verified step by step guidance

1. Identify the reactants and products in the reaction: solid calcium (Ca) reacts with hydrochloric acid (HCl), which is an aqueous acid that dissociates into H^+(aq) and Cl^-(aq) ions.
2. Write the balanced molecular equation for the reaction: calcium metal reacts with hydrochloric acid to produce calcium chloride (CaCl_2) in aqueous solution and hydrogen gas (H_2) as a product.
3. Write the complete ionic equation by breaking all strong electrolytes (like HCl and CaCl_2) into their ions: Ca(s) + 2H^+(aq) + 2Cl^-(aq) → Ca^{2+}(aq) + 2Cl^-(aq) + H_2(g).
4. Cancel the spectator ions that appear unchanged on both sides of the equation (in this case, Cl^- ions) to obtain the net ionic equation.
5. Write the net ionic equation showing only the species that undergo a chemical change: solid calcium reacts with hydrogen ions to form aqueous calcium ions and hydrogen gas, represented as \(Ca(s) + 2H^{+}(aq) \rightarrow Ca^{2+}(aq) + H_2(g)\).