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Some Basic Concepts of Chemistry question

2025 · 24 Jan · Shift 2 · Q6
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Some Basic Concepts of Chemistry question

2025 · 24 Jan · Shift 2 · Q6

JEE MainChemistrySome Basic Concepts of ChemistryMCQ+4 / −1
The elemental composition of a compound is 54.2%C,9.2%H54.2 \% \mathrm{C}, 9.2 \% \mathrm{H}54.2%C,9.2%H and 36.6%O36.6 \% \mathrm{O}36.6%O. If the molar mass of the compound is 132 g mol−1132 \mathrm{~g} \mathrm{~mol}^{-1}132 g mol−1, the molecular formula of the compound is : [Given : The relative atomic mass of C:H:O=12:1:16\mathrm{C}: \mathrm{H}: \mathrm{O}=12: 1: 16C:H:O=12:1:16 ]
  1. A
    C4H8O2\mathrm{C}_4 \mathrm{H}_8 \mathrm{O}_2C4​H8​O2​
  2. B
    C6H12O6\mathrm{C}_6 \mathrm{H}_{12} \mathrm{O}_6C6​H12​O6​
  3. C
    C4H9O3\mathrm{C}_4 \mathrm{H}_9 \mathrm{O}_3C4​H9​O3​
  4. D
    C6H12O3\mathrm{C}_6 \mathrm{H}_{12} \mathrm{O}_3C6​H12​O3​
View written solutionFree

Correct answer: D

  1. Assume 100 g of the compound so that the percentages become masses:
  • Carbon =54.2 g= 54.2\text{ g}=54.2 g
  • Hydrogen =9.2 g= 9.2\text{ g}=9.2 g
  • Oxygen =36.6 g= 36.6\text{ g}=36.6 g
  1. Convert masses into moles using atomic masses C=12\mathrm{C}=12C=12, H=1\mathrm{H}=1H=1, O=16\mathrm{O}=16O=16:

nC=54.212=4.5167n_\mathrm{C} = \frac{54.2}{12} = 4.5167nC​=1254.2​=4.5167

nH=9.21=9.2n_\mathrm{H} = \frac{9.2}{1} = 9.2nH​=19.2​=9.2

nO=36.616=2.2875n_\mathrm{O} = \frac{36.6}{16} = 2.2875nO​=1636.6​=2.2875

  1. Find the simplest mole ratio by dividing by the smallest value 2.28752.28752.2875:

nC2.2875=4.51672.2875≈1.975≈2\frac{n_\mathrm{C}}{2.2875} = \frac{4.5167}{2.2875} \approx 1.975 \approx 22.2875nC​​=2.28754.5167​≈1.975≈2

nH2.2875=9.22.2875≈4.02≈4\frac{n_\mathrm{H}}{2.2875} = \frac{9.2}{2.2875} \approx 4.02 \approx 42.2875nH​​=2.28759.2​≈4.02≈4

nO2.2875=1\frac{n_\mathrm{O}}{2.2875} = 12.2875nO​​=1

So the empirical formula is:

C2H4O\mathrm{C}_2\mathrm{H}_4\mathrm{O}C2​H4​O

  1. Calculate empirical formula mass:

2(12)+4(1)+16=24+4+16=442(12) + 4(1) + 16 = 24 + 4 + 16 = 442(12)+4(1)+16=24+4+16=44

  1. Use the molar mass to find the molecular formula:

Given molar mass =132 g mol−1=132\,\text{g mol}^{-1}=132g mol−1

Multiplier=13244=3\text{Multiplier} = \frac{132}{44} = 3Multiplier=44132​=3

Therefore molecular formula is:

(C2H4O)3=C6H12O3(\mathrm{C}_2\mathrm{H}_4\mathrm{O})_3 = \mathrm{C}_6\mathrm{H}_{12}\mathrm{O}_3(C2​H4​O)3​=C6​H12​O3​

  1. Check options:
  • A: C4H8O2\mathrm{C}_4\mathrm{H}_8\mathrm{O}_2C4​H8​O2​ has molar mass =88= 88=88 ❌
  • B: C6H12O6\mathrm{C}_6\mathrm{H}_{12}\mathrm{O}_6C6​H12​O6​ has molar mass =180= 180=180 ❌
  • C: C4H9O3\mathrm{C}_4\mathrm{H}_9\mathrm{O}_3C4​H9​O3​ has molar mass =105= 105=105 ❌
  • D: C6H12O3\mathrm{C}_6\mathrm{H}_{12}\mathrm{O}_3C6​H12​O3​ has molar mass =132= 132=132 ✅

Hence, the correct answer is Option D.

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