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MHT CET202520 Apr 2025Morning ShiftChemistryThermodynamics (C)Actual

Calculate the enthalpy of vaporisation of ethanol if 11.5 g of ethanol is completely vaporised by supplying 11.8 kJ of heat.

Options

  1. A21 7 ~kJ ~mol ⁻¹
  2. B47.2 ~kJ ~mol ⁻¹
  3. C65 1 ~kJ ~mol ⁻¹
  4. D39.0 ~kJ ~mol ⁻¹

Correct answer

B. 47.2 ~kJ ~mol ⁻¹

Step-by-step solution

The enthalpy of vaporization H_ vap represents the heat required to vaporize one mole of ethanol. Given that 11.8 kJ vaporizes 11.5 g of ethanol, we first determine the molar mass of ethanol as C₂H₅OH . The molar mass is 2 12.01 + 6 1.008 + 16.00 = 46.068 g/mol . The number of moles vaporized is 11.5 46.068 0.2496 mol . The enthalpy of vaporization is thus H_ vap = 11.8 0.2496 47.275 kJ/mol , which rounds to 47.2 kJ/mol .

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