1 g of water of volume 1 cm ³ at 100° C is converted into steam of same temperature under normal atmospheric pressure ( 10⁵ Pa). The volume of steam formed equals 1671 cm ³. If the latent heat of vaporisation of water is 2256 J/g, the change in internal energy is (a) 2423 J (b) 2089 J (c) 167 J (d) 2256 J

Answer: (b). First law: Δ U = Q - W, with Q = mL = 2256 J. W = PΔ V = 10⁵ × (1671 - 1) × 10⁻⁶ = 167 J Δ U = 2256 - 167 = 2089 J So the answer is (b) 2089 J.

1 g of water of volume 1 cm ³ at 100° C is converted into steam of… | MHT CET 2026 (14 May, Shift 1)

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Calorimetry, Latent Heat & Mechanical Equivalent of Heat

$1$ g of water of volume $1$ cm $^{3}$ at $100^{\circ}$ C is converted into steam of same temperature under normal atmospheric pressure ( $10^{5}$ Pa). The volume of steam formed equals $1671$ cm $^{3}$ . If the latent heat of vaporisation of water is $2256$ J/g, the change in internal energy is

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Answer: (b)

First law: $\Delta U = Q - W$ , with $Q = mL = 2256\text{ J}$ .
$W = P\Delta V = 10^5 \times (1671 - 1) \times 10^{-6} = 167\text{ J}$
$\Delta U = 2256 - 167 = 2089\text{ J}$
So the answer is (b) $2089\text{ J}$ .

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