Consider the following statements regarding matter : 1. Elements cannot be broken down into simpler substances. 2. A compound has variable composition and can be broken down into elements. 3. The solution of sulphur in carbon disulphide is an example of a homogeneous mixture. Which of the statements given above is/are not correct ?
- A.2 only
- B.1 and 3
- C.3 only
- D.1 and 2
Correct answer
Explanation
The correct answer is A, 2 only. Statement 2 is the only incorrect one, because a compound always has a fixed composition, not a variable one.
An element is the simplest form of matter and cannot be broken down into simpler substances by chemical reactions, so statement 1 is correct. A compound is formed when elements combine in a fixed ratio by mass; water is always hydrogen and oxygen in the ratio 1:8. It can be broken into its elements only by chemical means, such as electrolysis. A solution of sulphur in carbon disulphide has a uniform composition throughout, so it is a homogeneous mixture, and statement 3 is correct.
Option B is wrong because statements 1 and 3 are both correct. Option C is wrong because statement 3 is correct. Option D is wrong because statement 1 is correct.
Exam tip: compound means fixed ratio and new properties; mixture means variable ratio and parts keep their properties.
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