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Some Basic Concepts of Chemistry question

2022 · 26 Jun · Shift 2 · Q24
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Some Basic Concepts of Chemistry question

2022 · 26 Jun · Shift 2 · Q24

JEE MainChemistrySome Basic Concepts of ChemistryNumerical+4 / −1
The moles of methane required to produce 81 g of water after complete combustion is ‾×\underline{\hspace{2cm}}\times​× 10 −-− 2 mol. [nearest integer]
Numerical answer
View written solutionFree

Correct answer: 225

  1. Write the balanced combustion reaction of methane
CH4+2O2→CO2+2H2O\mathrm{CH_4 + 2O_2 \rightarrow CO_2 + 2H_2O}CH4​+2O2​→CO2​+2H2​O

From the balanced equation:

  • 111 mole of CH4\mathrm{CH_4}CH4​ produces 222 moles of H2O\mathrm{H_2O}H2​O.
  1. Find moles of water formed

Given mass of water = 81 g81\,\text{g}81g

Molar mass of water = 18 g mol−118\,\text{g mol}^{-1}18g mol−1

Moles of H2O=8118=4.5 mol\text{Moles of } H_2O = \frac{81}{18} = 4.5\,\text{mol}Moles of H2​O=1881​=4.5mol
  1. Use stoichiometric relation

Since

1 mol CH4→2 mol H2O1\,\text{mol CH}_4 \rightarrow 2\,\text{mol H}_2O1mol CH4​→2mol H2​O

So methane required for 4.54.54.5 mol water is

Moles of CH4=4.52=2.25 mol\text{Moles of CH}_4 = \frac{4.5}{2} = 2.25\,\text{mol}Moles of CH4​=24.5​=2.25mol
  1. Express in the required form

We need

2.25 mol=225×10−2 mol2.25\,\text{mol} = 225 \times 10^{-2}\,\text{mol}2.25mol=225×10−2mol

Hence the required integer is

225\boxed{225}225​
  1. Comparison with stored correct answer

Stored correct answer = 225225225

Our derived answer = 225225225

So the answer matches.

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