Consider the following statements : 1. Potassium carbonate is a salt of a weak acid and a weak base. 2. Ammonium nitrate is a salt of a strong acid and a weak base. 3. Ammonium acetate is a salt of a weak acid and a weak base. Which of the statements given above are correct?
- A.1 and 3 only
- B.2 and 3 only
- C.1 and 2 only
- D.1, 2 and 3
Correct answer
Explanation
The correct answer is B, 2 and 3 only. Potassium carbonate comes from a strong base and a weak acid, so statement 1 is wrong, while statements 2 and 3 are right.
A salt carries the character of the acid and base it is made from. Potassium carbonate, K2CO3, comes from potassium hydroxide, a strong base, and carbonic acid, a weak acid, so its solution is basic. Ammonium nitrate, NH4NO3, comes from nitric acid, a strong acid, and ammonium hydroxide, a weak base, so its solution is acidic. Ammonium acetate comes from acetic acid and ammonium hydroxide, both weak, and its solution is almost neutral.
A is wrong because it includes the false statement 1 and leaves out the true statement 2. C is wrong because it includes statement 1 and leaves out statement 3. D is wrong because statement 1 is false, since potassium hydroxide is a strong base.
Exam tip: strong acid + weak base = acidic salt (NH4Cl, NH4NO3); weak acid + strong base = basic salt (Na2CO3, K2CO3).
Practice Questions
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