Given: (I) aligned & H ₂( g )+ 1 2 O ₂( g ) H ₂ O (l) ; & H ^ _ 298 ~K =-285.9 ~kJ ~mol ⁻¹ aligned (II) aligned & H ₂( g )+ 1 2 O ₂( g ) H ₂ O ( g ); & H ^ _ 298 ~K =-241.8 ~kJ ~mol ⁻¹ aligned The molar enthalpy of vapourisation of water wi

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Given: (I) aligned & H ₂( g )+ 1 2 O ₂( g ) H ₂ O (l) ; & H ^ _ 298 ~K =-285.9 ~kJ ~mol ⁻¹ aligned (II) aligned & H ₂( g )+ 1 2 O ₂( g ) H ₂ O ( g ); & H ^ _ 298 ~K =-241.8 ~kJ ~mol ⁻¹ aligned The molar enthalpy of vapourisation of water will be :

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Correct answer: A. 241.8 ~kJ ~mol ⁻¹

Given H ₂( g )+ 1 2 O ₂(g) H ₂ O (l) ; H ^ =-285.9 ~kJ ~mol ⁻¹ (1) H ₂( g )+ 1 2 O ₂(g) H ₂ O (g) ; H ^ =-241.8 ~kJ ~mol ⁻¹ (2) We have to calculate H ₂ O (l) H ₂ O ( g ) ; H ^ = ? On substracting eqn. (2) from eqn. (1) we get H ₂ O (l) H ₂ O ( g ) ; H ^ =-241.8-(-285.9)=44.1 ~kJ ~mol ⁻¹

Given: (I) aligned & H ₂( g )+ 1 2 O ₂( g ) H ₂ O (l) ; & H ^ _ 298 ~K =-285.9 ~kJ ~mol ⁻¹ aligned (II) aligned & H ₂( g )+ 1 2 O ₂( g ) H ₂ O ( g ); & H ^ _ 298 ~K =-241.8 ~kJ ~mol ⁻¹ aligned The molar enthalpy of vapourisation of water will be :

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