Engineering Questions with Answers - Multiple Choice Questions

# Materials Science MCQ’s – Gibbs Phase Rule

1 - Question

What is Gibbs phase rule for general system?
a) P = C – 1 – F
b) P = C + 1 – F
c) P + F = C – 2
d) P + F = C + 2
Explanation: The number of degrees of freedom, F (no. of independently variable factors), number of components, C, and number of phases in equilibrium, P.

2 - Question

What is Gibbs phase rule for metallurgical system?
a) F = C – 1 – P
b) F = C + 1 – P
c) P + F = C – 2
d) P + F = C + 2
Explanation: For metallurgical system pressure has no appreciable effect on phase equilibrium and hence, F = C – P + 1.

3 - Question

In a single – component condensed system, if degree of freedom is zero, maximum number of phases that can co – exist _________
a) 2
b) 3
c) 0
d) 1
Explanation: Given F = 0
Then p = c + 1, c = 1
.: P = 2.

4 - Question

The degree of freedom at a triple point in the unary diagram for water is ________
a) 2
b) 3
c) 0
d) 1
Explanation: For three phase system degree of freedom is 0.

5 - Question

What is degree of freedom for single – phase fields on the phase diagram?
a) 2
b) 3
c) 0
d) 1
Explanation: F = C + 1 – P
F = 3 – P (C = 2)
.:F = 2.

6 - Question

What is degree of freedom when two phases co – exist?
a) 2
b) 3
c) 0
d) 1
Explanation: F = C + 1 – P
F = 3 – P (C = 2)
F = 3 – 2 = 1.

7 - Question

What is degree of freedom when three phases co – exist?
a) 2
b) 3
c) 0
d) 1
Explanation: F = C + 1 – P
F = 3 – P (C = 2)
F = 3 – 3 = 0.

8 - Question

For single component system when degree of freedom is 1(one) then number of phases _______
a) 2
b) 3
c) 0
d) 1
Explanation: F = C + 1 – P
F = 2 – P (C = 1)
→ p = 2 – F = 2 – 1 = 1.

9 - Question

When α, L and β phase fields touch the isotherm line what are the respective phase compositions? a) 8.0 wt%, 71.9 wt%, 91.2 wt% of Ag
b) 8.0 wt%, 91.2 wt%, 71.9 wt% of Ag
c) 71.9 wt%, 91.2 wt%, 8.0 wt% of Ag
d) 91.2 wt%, 8.0 wt%, 71.9 wt% of Ag

Explanation: For binary systems, when three phases are present, there will be F = 0, so composition is fixed.

10 - Question

For binary alloy consisting of three phases of non – equilibrium one, What will be the temperature of these phases? a) Different
b) Constant
c) Same
d) Two of them will be with one temperature