Question

A 1.84 mg sample of polyhydric alcoholic compound ‘X’ of molar mass 92.0 g/mol gave 1.344 mL of H₂ gas at STP. The number of alcoholic hydrogens present in compound ‘X’ is____.

Answer 1

Correct Answer: 6

To determine the number of alcoholic hydrogens in compound 'X', follow these steps:

1. Calculate Moles of H₂ Gas: At STP, 1 mole of any gas occupies 22.4 L. Therefore, the moles of H₂ is given by:
Moles of H₂ = 1.344 mL × (1 L/1000 mL) / 22.4 L/mol ≈ 0.00006 mol.

2. Relate Moles of 'X' and H₂ Gas: The moles of 'X' can be calculated using its mass and molar mass:
Moles of 'X' = 1.84 mg × (1 g/1000 mg) / 92.0 g/mol ≈ 0.00002 mol.

3. Determine the Number of Alcoholic Hydrogens: Since 1 mole of 'X' corresponds to 0.00002 mol and produces 0.00006 mol of H₂, each molecule of 'X' must have:
Alcoholic hydrogens = (0.00006 mol H₂ / 0.00002 mol 'X') = 3 H₂ per molecule of 'X'.

4. Calculate Total Alcoholic Hydrogen Atoms: To produce 3 moles of H₂, 'X' must have 6 alcoholic hydrogen atoms.

The number of alcoholic hydrogens in the compound 'X' is 6, which is within the expected range (6,6).