Reaction with Carbonates

Carboxylic acids are strong enough acids to react with carbonates and hydrogencarbonates, forming a salt, water and carbon dioxide. You see effervescence (fizzing), and the gas turns limewater cloudy.2CH₃COOH + Na₂CO₃ → 2CH₃COONa + H₂O + CO₂
CH₃COOH + NaHCO₃ → CH₃COONa + H₂O + CO₂The ionic equation for the carbonate reaction is:2H⁺ + CO₃²⁻ → H₂O + CO₂The salts are named with the ending -oate: ethanoic acid gives sodium ethanoate, CH₃COONa (containing the CH₃COO⁻ ion), and propanoic acid gives sodium propanoate.A test for carboxylic acids: add solid sodium hydrogencarbonate or sodium carbonate solution. Effervescence, with a gas that turns limewater cloudy, shows a carboxylic acid. Alcohols are not acidic enough to react, so they give no fizzing. This distinguishes a carboxylic acid from an alcohol.Worked example: 0.0200 mol of ethanoic acid reacts with excess sodium carbonate. The ratio is 2CH₃COOH : 1CO₂, so 0.0100 mol of CO₂ forms. The mass of CO₂ (M_r = 44.0) is 0.0100 × 44.0 = 0.440 g.