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Which one of the following statements is correct when saturation pressure of water vapour increases?

Which one of the following statements is correct when saturation pressure of water vapour increases? Correct Answer Enthalpy of evaporation decreases

Concept:

As the saturation pressure of water vapour increases saturation temperature of water vapour increases, moisture quality i.e. dryness fraction of the water vapour decreases and the enthalpy of evaporation or vaporization decreases as seen from the T – S curve.

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For line 1 at pressure P1, hfg = hg – hf

And for line 2 at pressure P2, hfg = hg – hf thus from T – S diagram for two lines as P2 > P1 the difference of enthalpy between the saturated vapour and saturated liquid i.e. hfg decreases.

With the increase in saturation pressure the enthalpy of evaporation continuously decreases up to the critical point and at critical point enthalpy of evaporation becomes zero.

Above the critical temperature, the liquid and vapour phases are indistinguishable, and the substance is called a supercritical fluid. And the critical point of the substance is the highest temperature and pressure at which a gas and a liquid can coexist at equilibrium.

Related Questions

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