112 ml of a gas is produced at S.T.P. by the action of 412 mg of alcohol ROH with CH3MgI. The molecular mass of alcohol is:
Correct answer: C. 82.4 g
- A. 32 g
- B. 41.2 g
- C. 82.4 g
- D. 156 g
Explanation
The correct answer is 82.4 g. The reaction between the alcohol ROH and CH3MgI produces CH4 as a gas. At STP, 22.4 liters of gas is equivalent to one mole of CH4. Given that 112 ml (0.112 liters) of CH4 is produced, this represents 0.112/22.4 moles of CH4. Since 412 mg (0.412 g) of alcohol produces this amount of CH4, the molar mass of alcohol is calculated as 0.412 g divided by 0.112/22.4, which equals 82.4 g. Other options are incorrect as they do not match this stoichiometric calculation.
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