Question

0.01 mole of an organic compound (X) containing 10% hydrogen, on complete combustion, produced 0.9 g H₂O. Molar mass of (X) is ___________g mol\(^{-1}\).

Hint:

The amount of hydrogen in a compound can be determined from the water produced in combustion. Use stoichiometry to find the molar mass.

Answer 1

Correct Answer: 100

Given that the compound contains 10% hydrogen, we can assume the molar mass of the compound is \( M_X \). - Mass of hydrogen in 0.01 mole of X = \( 0.01 \times 10 = 0.1 \text{g} \). 
- In the complete combustion of X, the hydrogen reacts with oxygen to form H₂O. 
- The number of moles of water formed is \( \frac{0.9}{18} = 0.05 \text{moles} \).
- In 1 mole of H₂O, there are 2 moles of hydrogen atoms. So, the moles of hydrogen atoms that reacted are \( 2 \times 0.05 = 0.1 \text{moles} \). The number of moles of hydrogen in 0.01 mole of X is 0.1 g, which gives the molar mass of X as: \[ \text{Molar Mass of X} = \frac{\text{Mass of X}}{\text{Number of moles of X}} = \frac{0.01}{0.01} = 100 \text{ g/mol}. \] Thus, the molar mass of X is 100 g/mol.

Answer 2

Problem:

0.01 mole of an organic compound (X) containing 10% hydrogen, on complete combustion, produced 0.9 g of H₂O. Find the molar mass of compound (X).

Given:

Moles of compound \( X = 0.01 \, \text{mol} \)

Hydrogen content = 10% by mass

Mass of water produced = \( 0.9 \, \text{g} \)

Step 1: Moles of Water Produced

Molar mass of water \( H_2O = 18 \, \text{g/mol} \)

\[ \text{Moles of } H_2O = \frac{0.9}{18} = 0.05 \, \text{mol} \]

Step 2: Mass of Hydrogen in Water

Each mole of water contains 2 grams of hydrogen.

\[ \text{Mass of hydrogen} = 0.05 \times 2 = 0.1 \, \text{g} \]

Step 3: Use Percentage to Find Molar Mass

If 0.1 g of hydrogen is 10% of the mass of 0.01 mol of X:

\[ \frac{0.1}{0.01 \times M} = 0.10 \]

Solving:

\[ 0.1 = \frac{0.1}{0.01M} \Rightarrow 0.01M = \frac{0.1}{0.1} = 1 \Rightarrow M = \frac{1}{0.01} = 100 \]

Final Answer:

\[ \boxed{\text{Molar mass of } X = 100 \, \text{g/mol}} \]