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Some Basic Concepts of Chemistry question

2021 · 18 Mar · Shift 1 · Q20
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Some Basic Concepts of Chemistry question

2021 · 18 Mar · Shift 1 · Q20

JEE MainChemistrySome Basic Concepts of ChemistryNumerical+4 / −1
A reaction of 0.1 mole of Benzylamine with bromomethane gave 23 g of Benzyl trimethyl ammonium bromide. The number of moles of bromomethane consumed in this reaction are n ×\times× 10 −-− 1, when n = ‾\underline{\hspace{2cm}}​. (Round off to the Nearest Integer). (Given : Atomic masses : C : 12.0 u, H : 1.0 u, N : 14.0 u, Br : 80.0 u]
Numerical answer
View written solutionFree

Correct answer: 3

  1. Identify the product and its formula

Benzylamine is: C6H5CH2NH2=C7H9N\mathrm{C_6H_5CH_2NH_2} = \mathrm{C_7H_9N}C6​H5​CH2​NH2​=C7​H9​N

Benzyl trimethyl ammonium bromide is formed by replacing the three H atoms on nitrogen by three methyl groups: C6H5CH2N(CH3)3Br\mathrm{C_6H_5CH_2N(CH_3)_3Br}C6​H5​CH2​N(CH3​)3​Br

Its molecular formula is: C10H16NBr\mathrm{C_{10}H_{16}NBr}C10​H16​NBr

  1. Calculate molar mass of benzyl trimethyl ammonium bromide

M=10(12)+16(1)+14+80M = 10(12) + 16(1) + 14 + 80M=10(12)+16(1)+14+80 =120+16+14+80=230 g mol−1= 120 + 16 + 14 + 80 = 230\ \text{g mol}^{-1}=120+16+14+80=230 g mol−1

  1. Calculate moles of product formed

Given mass of product = 23 23\,23g

moles of product=23230=0.1 mol\text{moles of product} = \frac{23}{230} = 0.1\ \text{mol}moles of product=23023​=0.1 mol

  1. Relate bromomethane consumed to product formed

To convert benzylamine to benzyl trimethyl ammonium bromide, nitrogen gets three methyl groups from three molecules of bromomethane:

C6H5CH2NH2+3CH3Br→[C6H5CH2N(CH3)3]Br+2HBr\mathrm{C_6H_5CH_2NH_2 + 3CH_3Br \rightarrow [C_6H_5CH_2N(CH_3)_3]Br + 2HBr}C6​H5​CH2​NH2​+3CH3​Br→[C6​H5​CH2​N(CH3​)3​]Br+2HBr

So, for every 1 mole of product formed, bromomethane consumed = 3 moles.

Since product formed is 0.10.10.1 mol, moles of CH3Br=3×0.1=0.3 mol\text{moles of } \mathrm{CH_3Br} = 3 \times 0.1 = 0.3\ \text{mol}moles of CH3​Br=3×0.1=0.3 mol

  1. Match with the given form

Given: moles of bromomethane consumed=n×10−1\text{moles of bromomethane consumed} = n \times 10^{-1}moles of bromomethane consumed=n×10−1

We found: 0.3=3×10−10.3 = 3 \times 10^{-1}0.3=3×10−1

Hence, n=3n = 3n=3

Comparison with stored answer: Stored correct answer is 333, which matches our result.

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