This set of Engineering Chemistry Multiple Choice Questions & Answers (MCQs) focuses on “Two Component System”.
1. What is the definition of a lower critical temperature?
a) The minimum temperature at which equilibrium is achieved
b) The lowest temperature at which two components will attain vapor state
c) The lowest temperature at which two components sublimates
d) The lowest temperature at which two components form a mixture
View Answer
Explanation: The lower critical solution temperature is the lowest temperature at which two components are insoluble and attains equilibrium. Conversely, the upper critical solution temperature is the highest temperature at which two components are soluble as single phase.
2. With reference to a two component system, a vapor line indicates ________
a) A region where the temperature and pressure remains stable
b) A region where the solubility remains constant
c) An area below which components do not mingle
d) An area above which both the components mingle to form a single mixture
View Answer
Explanation: A vapor line is another name for an isotherm. It represents constant temperature and constant pressure relation at which the equilibrium is obtained. A vapor line helps in finding out equilibrium concentrations.
3. With reference to a two component system, an isobar indicates _______
a) A region where the temperature remains constant
b) An area below phase end products remains
c) An area above which only the liquid vapors remains
d) A region where the composition lies in equilibrium
View Answer
Explanation: An isobar is a line that indicates a region where the composition remains constant and in the equilibrium state. In a two component solid-liquid system, it is drawn vertically covering a wide range of temperatures.
4. Which of the following statements is not true for a system that has reached the eutectic temperature?
a) The system is a open system
b) The system is a miscible fluid
c) Components lie in liquid state
d) A region between sublimation and eutectic curve lies stable
View Answer
Explanation: The eutectic temperature is achieved by heating a liquid in the point where the density of the liquid state is equal to the density of the vapor state. Here, the interface between the liquid and vapor vanishes resulting in a miscible fluid. This can only occur in a closed system (otherwise the vapor would escape into the surroundings).
5. What does the term “ metastable” indicate?
a) A place where the composition of the system remains constant
b) A place where the pressure remains constant with low value
c) An area below which a vapor- liquid mixture is obtained
d) A region where the temperature remains constant
View Answer
Explanation: A metastable is a line that indicates a place where the temperature remains constant. In a two component system it is drawn horizontally covering a wide range of compositions.
6. Which of the following statements are correct about the equilibrium point on a two component system?
a) All the compounds are liquid
b) The boiling point of the mixture is less than the boiling points of the individual compounds
c) The degree of freedom is 0
d) Invariant reaction takes place
View Answer
Explanation: The Eutectic point on a phase diagram is a point at which the mixture boils at a temperature lower than that of the pure substances. The substance attains equilibrium state.
7. During metastable state, the size of the particle_________
a) Increases
b) Decreases
c) Won’t change
d) Not related
View Answer
Explanation: Since for a system to be in equilibrium condition, its size automatically increases by Mond’s effect which is why the particle’s size increases during metastable state due to changes in molecular size.
8. Which of the following is not responsible for phase deposition?
a) Container wall
b) Grain size
c) Stacking effect
d) Disjoints
View Answer
Explanation: Under equilibrium conditions, the molecules adhere to the center of the container and under non-equilibrium conditions, the vapors are let out through the walls of the container hence the container wall has no role to play in the reaction.
9. Where does the particle growth occur?
a) Movement of grains
b) Movement of equilibrium liquid
c) Equilibrium mixture
d) Non equilibrium mixture
View Answer
Explanation: During diffusion process in the transformation of solid to vapor state, the molecules move from regions of higher concentration to regions of lower concentrations and hence growth takes place n a controlled way.
10. Overall transformation rate changes with temperature as follows under what condition?
a) Decreases
b) Increases then decreases
c) Follows a linear path
d) Increases with temperature
View Answer
Explanation: According to the phase graph, at the solidus region, the temperature is high. As the melting point increases, the temperature decreases and vice versa (applicable to all component systems).
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