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Some Basic Concepts of Chemistry question

2016 · 9 Apr · Shift 1 · Q7
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Some Basic Concepts of Chemistry question

2016 · 9 Apr · Shift 1 · Q7

JEE MainChemistrySome Basic Concepts of ChemistryMCQ+4 / −1
An organic compound contains C, H and S. The minimum molecular weight of the compound containing 8% sulphur is : (atomic weight of S = 32 amu)
  1. A
    200 g mol −-− 1
  2. B
    400 g mol −-− 1
  3. C
    600 g mol−1
  4. D
    300 g mol−1
View written solutionFree

Correct answer: B

  1. Let the molecular mass of the compound be MMM.

  2. The compound contains sulphur, and the minimum molecular mass will occur when the molecule contains the smallest possible number of sulphur atoms, i.e. one sulphur atom.

  3. Mass percent of sulphur is given as 8%8\%8%: mass of S in one moleculemolecular mass×100=8\frac{\text{mass of S in one molecule}}{\text{molecular mass}} \times 100 = 8molecular massmass of S in one molecule​×100=8

    With one sulphur atom: 32M×100=8\frac{32}{M} \times 100 = 8M32​×100=8

  4. Solve for MMM: 3200M=8\frac{3200}{M} = 8M3200​=8 M=32008=400M = \frac{3200}{8} = 400M=83200​=400

  5. Therefore, the minimum molecular weight is: 400 g mol−1400\ \text{g mol}^{-1}400 g mol−1

  6. Checking options:

    • A: 200200200 ❌
    • B: 400400400 ✅
    • C: 600600600 ❌
    • D: 300300300 ❌

Hence, the correct option is B.

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