## Engineering Chemistry MCQ (Application of Phase Rule)

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Application of Phase Rule to One Component System

**1. Which of the following equilibriums can phase rule be applies to?**

a) Isometric

b) Isobaric

c) Isometric and Isobaric

d) Mechanical

Answer: c

Explanation: Since phase rule can be applied to factors like solubility, concentration,

reversibility of reaction, temperature, pressure, molecular weight, atomic weight,

strength of molecules etc (since these parameters are applicable for isometric and

isobaric states), phase rule can be applied to both isometric and isobaric equilibriums.

**2. What kind of particles can phase rule be applied to?**

a) Micro

b) Nano

c) Pico

d) Heavy particles

Answer: d

Explanation: Since the factors like solubility, concentration, reversibility of reaction,

temperature, pressure, molecular weight, atomic weight, strength of molecules etc

becomes negligible for microscopic particles, phase rule identifies only heavy particles.

**3. What kind of behavior can phase rule identify?**

a) Molecular behavior

b) Linear behavior

c) Curvic behavior

d) Atomic behavior

Answer: b

Explanation: In a general phase relation between temperature and concentration of

the component of various systems, the general graph will show a proportionate

relation between the two factors and hence phase rule identifies linear behavior.

**4. For Gibbs free energy along a system path for a transformation from state 1 to state 2, the reaction kinetics can be expressed by __________**

a) Rate = C exp(-ΔG1/RT)

b) Rate = C exp(-ΔG2/RT)

c) Rate = G/RT

d) Rate = RT/G

Answer: a

Explanation: In the above problem, we can see that the reactions coordinate

increases as the energy increases up to certain point above equilibrium and then it

gradually decreases. This system represents a system at stable point of time. Thus

according to energy phase relation, the rate of reaction is Rate = C exp(-ΔG1/RT).

**5. According to Gibbs phase rule for a 2-component system under condensed rule, what observation can be made within the equilibrium phase?**

a) T can be varied independently

b) Varying a T value fixes the equilibrium compositions

c) Neither T nor concentration can be varied respectively

d) 2 phases cannot coexist

Answer: b

Explanation: During invariant position of the system (equilibrium state), sometimes

due to increase in colligative properties of materials, the equilibrium faces a shift

slightly. In this case, the equilibrium can be brought back by varying T values.

**6. If the following conditions result in the formation of a regular solution?**

a) Ω = 0

b) Ω > 0

c) Ω < 0

d) Ω = 10

Answer: c

Explanation: We know that as the resistance increases, conductance decreases. This

happens at higher temperature and pressure. Thus a regular solution will be

formed only when conductivity of the solution is high. Thus the required condition is Ω < 0.

**7. With respect to the general phase diagram of two component system. Identify the type of solution formed at the eutectic point.**

a) Regular solution

b) Steady state solution

c) Invariant solution

d) Transition solution

Answer: a

Explanation: From the general phase diagram, the concentration of the first

component with respect to the other decreases till certain point (eutectic point) and

then increases gradually such that the other component’s concentration increases

together. Thus this is an example of regularity and hence a regular solution is obtained.

**8. With respect to the phase diagram of copper zinc system. There happens a phase transition at a particular point. There happens an equilibrium shift consequently. At which point will zinc reach its maximum concentration?**

a) Some point between transition and shift

b) After transition

c) Before shift

d) At the end of both transition and shift

Answer: d

Explanation: We know that all the transitions (equilibrium and phase transitions)

take place within the range 200 to 400 which is the normal equilibrium range.

According to Gibbs phase rule, zinc will reach its maximum concentration after

equilibrium point that is at the eutectic point.

**9. In the general phase diagram of water component system, the region that separates solid and liquid is called _______________**

a) Fusion curve

b) Sublimation curve

c) Metastable curve

d) Critical curve

Answer: b

Explanation: In a water component system, sometimes the water may not undergo

transition between solid to liquid instead directly gets converted from solid to

vapor. This is a stable state where a small variation in composition or temperature

may destroy the steadiness. This point is called sublimated curve.

**10. During an experiment, a slight variation causes deposition of the component in its solid state. From the given data, calculate the amount of component deposited. **

Temperature at equilibrium=0

Atmospheric temperature=217.7 k

Pressure=200 atm

a) 0.006

b) 0

c) 217.7

d) 100

Answer: b

Explanation: We know that according to Weiss law, concentration=

temperature/pressure (this law suits only for phase components). In this problem,

since the temperature corresponding to the deposition point is 0. Therefore, the

concentration is zero which means that ideally, no deposition has taken place.