An aqueous solution of sodium carbonate is alkaline because sodium carbonate is a salt of — Ionic Equilibrium Chemistry Question

💡 Solution & Explanation

# Solution: Why $Na_2CO_3$ Solution is Alkaline **Step 1: Identify the salt composition** $Na_2CO_3$ is formed from: - Strong base: $NaOH$ (sodium hydroxide) - Weak acid: $H_2CO_3$ (carbonic acid) **Step 2: Analyze hydrolysis in water** When $Na_2CO_3$ dissolves: $$Na_2CO_3 \rightarrow 2Na^+ + CO_3^{2-}$$ The $CO_3^{2-}$ ion undergoes hydrolysis: $$CO_3^{2-} + H_2O \rightleftharpoons HCO_3^- + OH^-$$ **Step 3: Determine pH character** Since $CO_3^{2-}$ is the conjugate base of a **weak acid** ($HCO_3^-$), it readily accepts protons from water, releasing $OH^-$ ions and making the solution **basic/alkaline**. **Conclusion:** $Na_2CO_3$ is a salt of a **strong base and weak acid**, which always produces an alkaline aqueous solution. **Why other options are wrong:** - Strong base + strong acid → neutral solution - Weak base + strong acid → acidic solution - Weak base + weak acid → depends on relative strengths