Question

17.0 g of NH₃ completely vapourises at –33.42°C and 1 bar pressure and the enthalpy change in the process is 23.4 kJ mol^–1. The enthalpy change for the vapourisation of 85 g of NH₃ under the same conditions is ______ kJ.

पर्याय

• 105

• 110

• 117

• 120

Answer 1

17.0 g of NH₃ completely vapourises at –33.42°C and 1 bar pressure and the enthalpy change in the process is 23.4 kJ mol^–1. The enthalpy change for the vapourisation of 85 g of NH₃ under the same conditions is 117 kJ.

Explanation:

17 g NH₃ contains 1 mol NH₃.

So, 85 g NH₃ will have `85/17` = 5 mol of NH₃

Enthalpy change for 1 mol of vaporisation of NH₃ = 23.4 kJ mol^–1

So, the enthalpy change required for 5 mol of vaporistion, ΔH = 5 mol × 23.4 kJ

= 117 kJ

Therefore, the enthalpy change for the vapourisation of 85 g of NH₃ under the same conditions is 117 kJ.