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JEE MainChemistryThermodynamics (C)

The magnitude of the heat of combustion of ethanol at constant volume is 1380 kJ mol ⁻¹ . When a certain mass of ethanol is completely burnt in a bomb calorimeter of heat capacity 15 kJ K ⁻¹ , the temperature of the calorimeter increases by 6 K . The mass of ethanol burnt is ______ g. (Given atomic masses: C = 12, H = 1, O = 16)

Correct answer

3

Step-by-step solution

Molar mass of ethanol ( C₂H₅OH ) = 2 12 + 6 1 + 16 = 46 g mol ⁻¹ Heat evolved during combustion = C T = 15 6 = 90 kJ Moles of ethanol burnt = Heat evolved Molar heat of combustion = 90 1380 = 3 46 mol Mass of ethanol burnt = Moles Molar mass = 3 46 46 = 3 g Answer: 3

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