JEE Advanced 2022 · Paper 1 · Chemistry Q6

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ChemistryNumerical+3Question 42 of 54

Consider the following reaction.

On estimation of bromine in 1.00 g of R using Carius method, the amount of AgBr formed (in g) is _____.

[Given: Atomic mass of H = 1, C = 12, O = 16, P = 31, Br = 80, Ag = 108]

(4-Bromophenyl)methanol → [red phosphorous, Br2] → R (major product).

Your answer

Answer and worked solution

Official answer: 1.49

R. Red P and $\ce{Br2}$ form $\ce{PBr3}$ , which converts the alcohol to 4-bromobenzyl bromide, $\ce{BrC6H4CH2Br}$ ( $M=250$ ). The aryl Br is not affected.

Carius estimation. 1.00 g of R is 0.004 mol and contains 0.008 mol Br. AgBr has $M=188$ :
$0.008\times188=1.50\ \text{g}.$

Topics:Qualitative and quantitative analysis of organic compounds Alcohols

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