JEE Main · 2021 · 24 Feb 2021 · Shift 2 · Some Basic Concepts of Chemistry

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1.86 g of aniline completely reacts to form acetanilide. 10% of the product is lost during purification. Amount of acetanilide obtained after purification (in g) is

____

\times 1 0^{- 2}

Answer: 243

Solution

Aniline

C_{6} H_{5} N H_{2}

has a molar mass of

93 g mo l^{- 1}

, so

1.86

g of it is

\frac{1.86}{93} = 0.02

mol. Acetylation replaces one hydrogen of the amino group by an acetyl group in a one-to-one ratio, so

0.02

mol of acetanilide

C_{6} H_{5} NHCOC H_{3}

is formed, and its molar mass is

135 g mo l^{- 1}

m = 0.02 \times 135 = 2.7 g

A tenth of this is lost on purification, leaving

0.9 \times 2.7 = 2.43

g, which in the units asked for is

243 \times 1 0^{- 2}

JEE Main · 2021 · 24 Feb 2021 · Shift 2 · Integer answer

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