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Some Basic Concepts of Chemistry question

2018 · 16 Apr · Shift 1 · Q11
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Some Basic Concepts of Chemistry question

2018 · 16 Apr · Shift 1 · Q11

JEE MainChemistrySome Basic Concepts of ChemistryMCQ+4 / −1
An unknown chlorohydrocarbon has 3.55% of chlorine. If each molecule of the hydrocarbon has one chlorine atom only; chlorine atoms present in 1 g of chlorohydrocarbon are : (Atomic wt. of Cl = 35.5 u; Avogadro constant = 6.023 ×\times× 1023 mol-1)
  1. A
    6.023 ×\times× 1020
  2. B
    6.023 ×\times× 109
  3. C
    6.023 ×\times× 1021
  4. D
    6.023 ×\times× 1023
View written solutionFree

Correct answer: A

  1. Given data

    • Chlorine percentage in the chlorohydrocarbon = 3.55%3.55\%3.55%
    • Mass of compound taken = 1 g1\,\text{g}1g
    • Atomic mass of chlorine = 35.5 u35.5\,\text{u}35.5u
    • Avogadro number = 6.023×1023 mol−16.023 \times 10^{23}\,\text{mol}^{-1}6.023×1023mol−1
    • Each molecule contains one chlorine atom.

  2. Mass of chlorine present in 1 g of compound Since chlorine is 3.55%3.55\%3.55% by mass, mass of Cl in 1 g compound=3.55100×1=0.0355 g\text{mass of Cl in 1 g compound} = \frac{3.55}{100} \times 1 = 0.0355\,\text{g}mass of Cl in 1 g compound=1003.55​×1=0.0355g

  3. Moles of chlorine atoms moles of Cl atoms=0.035535.5=0.001=10−3 mol\text{moles of Cl atoms} = \frac{0.0355}{35.5} = 0.001 = 10^{-3}\,\text{mol}moles of Cl atoms=35.50.0355​=0.001=10−3mol

  4. Number of chlorine atoms number of Cl atoms=10−3×6.023×1023\text{number of Cl atoms} = 10^{-3} \times 6.023 \times 10^{23}number of Cl atoms=10−3×6.023×1023 =6.023×1020= 6.023 \times 10^{20}=6.023×1020

  5. Relation to number of molecules Since each molecule has exactly one chlorine atom, the number of chlorine atoms present is exactly the same as the number of molecules corresponding to those chlorine atoms.

  6. Compare with options

    • A: 6.023×10206.023 \times 10^{20}6.023×1020 ✅
    • B: 6.023×101096.023 \times 10^{109}6.023×10109 ❌
    • C: 6.023×10216.023 \times 10^{21}6.023×1021 ❌
    • D: 6.023×10236.023 \times 10^{23}6.023×1023 ❌

Therefore, the correct option is A.

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