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# Calculate the Entropy Change in Surroundings When 1.00 Mol of H2o(L) Is Formed Under Standard Conditions. - CBSE (Science) Class 11 - Chemistry

ConceptEnthalpy Change, ∆_rH of a Reaction - Reaction Enthalpy Standard Enthalpy of Reactions

#### Question

Calculate the entropy change in surroundings when 1.00 mol of H2O(l) is formed under standard conditions. ΔfHθ = –286 kJ mol–1.

#### Solution 1

It is given that 286 kJ mol–1 of heat is evolved on the formation of 1 mol of H2O(l). Thus, an equal amount of heat will be absorbed by the surroundings.

qsurr = +286 kJ mol–1

Entropy change (ΔSsurr) for the surroundings = q_"surr"/7

= (286 kJ mol^(-1))/298 k

∴ ΔSsurr = 959.73 J mol–1 K–1

#### Solution 2

q_"rev" = (-triangle_f H^(Theta)) = - 286 kJ mol^(-1) = 286000 J mol^(-1)

triangleS_(("Surroundings")) = q_"rev"/T = (286000 J mol^(-1))/(298 K) = 959 J K^(-1) mol^(-1)

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Solution Calculate the Entropy Change in Surroundings When 1.00 Mol of H2o(L) Is Formed Under Standard Conditions. Concept: Enthalpy Change, ∆_rH of a Reaction - Reaction Enthalpy - Standard Enthalpy of Reactions.
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