This set of Thermodynamics Multiple Choice Questions & Answers (MCQs) focuses on “P-V diagram for Pure Substance”.
1. Which of the following is a property of a pure substance?
a) it has constant chemical composition throughout its mass
b) it is a one-component system
c) it may exist in one or more phases
d) all of the mentioned
View Answer
Explanation: These are some of the properties of a pure substance.
2. For water, as temperature increases, volume always increases?
a) true
b) false
View Answer
Explanation: From 0 degree Celsius to 4 degree Celsius as temperature increases, volume of water decreases which is a peculiarity of water.
3. A saturation state is a state from which a change of phase may occur
a) without a change of pressure or temperature
b) with a change of pressure or temperature
c) both of the mentioned
d) none of the mentioned
View Answer
Explanation: For example, water at 0 degree Celsius and at 100 degree Celsius.
4. In which of the following state does water exist?
a) saturated solid state
b) saturated liquid state
c) saturated vapour state
d) all of the mentioned
View Answer
Explanation: Water exists in these states at 0 degree Celsius and at 100 degree Celsius.
5. Which of the following exists in a p-V diagram for water?
a) saturated solid line
b) saturated liquid lines
c) saturated vapour line
d) all of the mentioned
View Answer
Explanation: The p-V diagram for water has all these three lines.
6. The triple point is a line on the p-V diagram, where all the three phases, solid, liquid and gas exist.
a) true
b) false
View Answer
Explanation: At triple point, all these three phases exists in equilibrium.
7. At a pressure below the triple point line,
a) the substance cannot exist in the liquid phase
b) the substance when heated transforms from solid to vapour
c) both of the mentioned
d) none of the mentioned
View Answer
Explanation: This phenomenon is known as sublimation and takes place by absorbing the latent heat of sublimation from the surroundings.
8. Which of the following statement is true?
a) to the left of saturated solid line is the solid region
b) between saturated solid line and saturated liquid line with respect to solidification there exists the solid-liquid mixture region
c) between two saturated liquid lines is the compressed liquid region
d) all of the mentioned
View Answer
Explanation: These statements come from the p-V diagram for a pure substance.
9. The isotherm passing through the critical point is called the critical isotherm.
a) true
b) false
View Answer
Explanation: At critical point, all the quantities like pressure, temperature and volume attain their critical values.
10. The greater the temperature, the ____ is the vapour pressure.
a) lower
b) higher
c) depends on the substance
d) none of the mentioned
View Answer
Explanation: The vapour pressure mainly depends on the temperature.
11. Phase change occurs at
a) constant pressure
b) constant temperature
c) constant pressure and temperature
d) none of the mentioned
View Answer
Explanation: For phase change, pressure and temperature must be constant like water at 0 degree Celsius and at 100 degree Celsius.
12. Which of the following statement is true?
a) saturation temperature is a function of pressure
b) saturation pressure is a function of temperature
c) both of the mentioned
d) none of the mentioned
View Answer
Explanation: At saturation temperature, a pure liquid transforms into vapour and at saturation pressure, the liquid boils.
Sanfoundry Global Education & Learning Series – Thermodynamics.
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