QJEEM07Ch5f19: JEE Main 2007 Chemistry - Class 11 JEEM07Ch5f19 Solution: Assuming that water vapour is an ideal gas, the internal energy …

Question

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Assuming that water vapour is an ideal gas, the internal energy change

(Δ U)

when

1

mol of water is vapourised at

1

bar pressure and

100^{\circ} C

(Given : molar enthalpy of vapourisation of water at

1

bar and

373

K

= 41 k J m o l^{- 1}

and

R = 8.3 J m o l^{- 1} K^{- 1}

)

Accepted Answer

Given

Δ H = 41 k J m o l^{- 1}

= 41000 J m o l^{- 1}

T = 100^{\circ} C = 273 + 100

= 373 K, n = 1

Δ U = Δ H - Δ n R T

= 41000 - (2 \times 8.314 \times 373)

= 37898.88 J m o l^{- 1}

= 37.9 k J m o l^{- 1}

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