Thermodynamics (Properties of Pure Substances)

Choose the correct answer
1.         (a) Specific volume of water decreases on freezing
(b) Boiling point of water decreases with increasing pressure
(c) Specific volume of CO2 increases on freezing
(d) Freezing temperature of water decreases with increasing pressure.

2.         (a) The slope of vaporisation curve is always negative
(b) The slope of vapourization curve is always positive
(c) The slope of sublimation curve in negative for all pure substances
(d) The slope of fusion curve is positive for all pure substances.

3.         (a) The process of passing from liquid to vapour is condensation
(b) An isothermal line is also a constant pressure line during wet region
(c) Pressure and temperature are independent during phase change
(d) The term dryness fraction is used to describe the fraction by mass of liquid in the mixture of liquid water and water vapour.

4.         The latent heat of vaporisation at critical point is
(a) less than zero
(b) greater than zero
(c) equal to zero
(d) none of the above.

5.         (a) Critical point involves equilibrium of solid and vapour phases
(b) Critical point involves equilibrium of solid and liquid phases
(c) Critical point involves equilibrium of solid, liquid and vapour phases
(d) Triple point involves equilibrium of solid, liquid and vapour phases.

6.         With the increase in pressure
(a) boiling point of water increases and enthalpy of evaporation increases
(b) boiling point of water increases and enthalpy of evaporation decreases
(c) boiling point of water decreases and enthalpy of evaporation increases.

7.         With increase in pressure
(a) enthalpy of dry saturated steam increases
(b) enthalpy of dry saturated steam decreases
(c) enthalpy of dry saturated steam remains same
(d) enthalpy of dry saturated steam first increases and then decreases.

8.         Dryness fraction of steam is defined as
(a) mass of water vapour in suspension/(mass of water vapour in suspension + mass of dry steam)
(b) mass of dry steam/mass of water vapour in suspension
(c) mass of dry steam/(mass of dry steam + mass of water vapour in suspension)
(d) mass of water vapour in suspension/mass of dry steam.

9.         The specific volume of water when heated at 0°C
(a) first increases and then decreases
(b) first decreases and then increases
(c) increases steadily (d) decreases steadily.

10.       Only throttling calorimeter is used for measuring
(a) very low dryness fraction upto 0.7
(b) very high dryness fraction upto 0.98
(c) dryness fraction of only low pressure steam
(d) dryness fraction of only high pressure steam.

Answers:
1. (d)
2. (a)
3. (b)
4. (c)
5. (d)
6. (b)
7. (b)
8. (c)
9. (b)
10. (b)

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