iGCSE Chemistry (0620) Core:11.7 Carboxylic acids: Exam Style Questions Paper 1- New Syllabus
▶️ Answer/Explanation
Detailed solution:
Ethanoic acid reacts with reactive metals like sodium to produce a salt and hydrogen gas: $2\text{CH}_3\text{COOH} + 2\text{Na} \rightarrow 2\text{CH}_3\text{COONa} + \text{H}_2$. The salt formed is sodium ethanoate (Q). If P were sodium oxide (a base), the reaction would be: $2\text{CH}_3\text{COOH} + \text{Na}_2\text{O} \rightarrow 2\text{CH}_3\text{COONa} + \text{H}_2\text{O}$, producing water, not hydrogen. Since hydrogen is produced as shown in the equation, P must be a reactive metal, sodium, and Q is the salt sodium ethanoate. So option B correctly identifies P as sodium and Q as sodium ethanoate.
▶️ Answer/Explanation
Detailed solution:
Ethanoic acid is a weak acid, so its pH is around 3 to 4, not 10 which would be an alkaline pH. Statement 1 is false. As an acid, it does react with metal carbonates in a classic fizzing reaction that produces carbon dioxide gas, a salt, and water, so statement 2 is true. It also reacts with reactive metals like magnesium to give off hydrogen gas, just like any other acid, so statement 3 is also true. Therefore, only statements 2 and 3 are correct.
▶️ Answer/Explanation
Detailed solution:
Ethanoic acid is a weak acid but still shows typical acid reactions. With reactive metals like magnesium, it produces a salt (magnesium ethanoate) and hydrogen gas: $2\mathrm{CH_3COOH + Mg \rightarrow (CH_3COO)_2Mg + H_2}$. Option A is wrong because acids react with carbonates to give salt, water, and carbon dioxide—not hydrogen. Option B is incorrect because acids react with metal oxides to form salt and water only, not oxygen. Option D is wrong because acids turn blue litmus paper red, not the other way around; red litmus turning blue indicates a base or alkali. So the only correct statement is that ethanoic acid reacts with reactive metals to produce a salt and hydrogen gas.