JEE Main 2022 · 29 Jul · Shift 2 · Chemistry Q88

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ChemistryInteger+4 / -1Question 88 of 90

A 1.84 mg sample of polyhydric alcoholic compound 'X' of molar mass 92.0 g/mol gave 1.344 mL of H $_2$ gas at STP. The number of alcoholic hydrogens present in compound 'X' is _______.

Your answer

Answer and worked solution

Official answer: 3

Intended compound. A polyhydric alcohol of molar mass 92 is glycerol, $\mathrm{C_3H_5(OH)_3}$ : three alcoholic hydrogens, as keyed.

About the numbers. Taken literally, $\frac{1.84\times10^{-3}}{92}=2\times10^{-5}$ mol of X and $\frac{1.344}{22400}=6\times10^{-5}$ mol of H₂ would mean 6 OH per molecule, which no compound of molar mass 92 can have; glycerol would give 0.672 mL. The data are inconsistent, and the answer follows the compound.

Answer: 3

Topics:Alcohols Mole concept

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JEE Main 2022 · 29 Jul · Shift 2, Chemistry question 88