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Some Basic Concepts of Chemistry question

2003 · Shift 0 · Q53
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Some Basic Concepts of Chemistry question

2003 · Shift 0 · Q53

JEE MainChemistrySome Basic Concepts of ChemistryMCQ+4 / −1
What volume of hydrogen gas at 273 K and 1 atm pressure will be consumed in obtaining 21.6 g of elemental boron (atomic mass = 10.8) from the reduction of boron trichloride by hydrogen?
  1. A
    67.2 L
  2. B
    44.8 L
  3. C
    22.4 L
  4. D
    89.6 L
View written solutionFree

Correct answer: A

  1. Write the balanced chemical reaction

Reduction of boron trichloride by hydrogen is:

2 BCl3+3 H2→2 B+6 HCl2\,\text{BCl}_3 + 3\,\text{H}_2 \rightarrow 2\,\text{B} + 6\,\text{HCl}2BCl3​+3H2​→2B+6HCl

  1. Find moles of boron produced

Given mass of boron = 21.6 g21.6\,\text{g}21.6g

Atomic mass of boron = 10.8 g mol−110.8\,\text{g mol}^{-1}10.8g mol−1

n(B)=21.610.8=2 moln(\text{B}) = \frac{21.6}{10.8} = 2\,\text{mol}n(B)=10.821.6​=2mol

  1. Use stoichiometry to find moles of hydrogen consumed

From the balanced equation:

2 mol B is produced from 3 mol H22\,\text{mol B} \text{ is produced from } 3\,\text{mol H}_22mol B is produced from 3mol H2​

So, for 222 mol boron, hydrogen required is:

n(H2)=3 moln(\text{H}_2) = 3\,\text{mol}n(H2​)=3mol

  1. Convert moles of hydrogen to volume at 273 K and 1 atm

At STP (273 K273\,\text{K}273K and 1 atm1\,\text{atm}1atm), 1 mole of any ideal gas occupies:

22.4 L22.4\,\text{L}22.4L

Thus,

V(H2)=3×22.4=67.2 LV(\text{H}_2) = 3 \times 22.4 = 67.2\,\text{L}V(H2​)=3×22.4=67.2L

  1. Match with the options

67.2 L67.2\,\text{L}67.2L corresponds to Option A.

Final Answer

A: 67.2 L67.2\,\text{L}67.2L

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