# Manufacturing Engineering Questions & Answers – Phase Diagram

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This set of Manufacturing Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Phase Diagram”.

1. Which of the following equation represents the Gibbs phase rule?
a) F = C + P + 2
b) F = C – P + 2
c) F = C + P + 1
d) F = C + P – 1

Explanation: The Gibbs phase rule is represented as: F = C – P + 2, where F = number of intensive degrees of freedom, P = number of phases and C = minimum number of independent constituents.

2. Number of degrees of freedom at a triple point in unary phase diagram is?
a) 1
b) 10
c) 0
d) -1

Explanation: A unary phase diagram has a single component thus, at triple point, the number of degrees of freedom, according to Gibbs phase rule F = 1 – 3 + 2 = 0.

3. The invariant reaction involving, a liquid phase decomposing into two different solids on cooling is known as _________
a) Eutectoid point
b) Eutectic point
c) Peritectic point
d) Peritectoid point

Explanation: The eutectic invariant reaction in general can be represented as:
L $$_{\overrightarrow{Cooling}}$$ S1 + S2
where, L represent the liquid of eutectic composition and S1 and S2 are two different solids of fixed composition each.
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4. The invariant reaction involving a solid phase decomposing into two different solids on cooling is known as ____________
a) Eutectoid point
b) Eutectic point
c) Peritectic point
d) Peritectoid point

Explanation: The eutectoid invariant reaction is a solid-state version of the eutectic reaction and in general, can be represented by an equation:
S1 $$_{\overrightarrow{Cooling}}$$ S2 + S3
where, S1, S2 and S3 are three different solids each of fixed composition.

5. The invariant reaction involving a liquid phase and a solid phase changing into a single solid phase on cooling is known as ____________
a) Eutectoid point
b) Eutectic point
c) Peritectic point
d) Peritectoid point

Explanation: A peritectic reaction in general can be represented by an equation:
L + S1 $$_{\overrightarrow{Cooling}}$$ S2
where, L represents a liquid of fixed composition, S1 and S2 are two different solids of fixed composition each.

6. The invariant reaction involving two solid phases changing into a single solid phase on cooling is known as ___________
a) Eutectoid point
b) Eutectic point
c) Peritectic point
d) Peritectoid point

Explanation: The peritectoid invariant reaction is a solid-state version of the peritectic reaction and in general, can be represented by an equation:
S1 + S2 $$_{\overrightarrow{Cooling}}$$ S3
where, S1, S2 and S3 are three different solids each of fixed composition.

7. For binary phase diagram Gibbs phase rule may be given as ____________
a) F = C + P + 2
b) F = C – P + 2
c) F = C – P + 1
d) F = C + P – 1

Explanation: Binary phase diagrams has two components. Apart from temperature and pressure, we will be having one composition variable for each of the phases in equilibrium. In order to simplify the Gibbs phase rule on paper (in 2D), binary phase diagrams are usually drawn at atmospheric pressure, showing variations in temperature and composition only. Pressure changes often produce no significant effect on the equilibrium and, therefore, it is customary to ignore the pressure variable and the vapour phase. The modified condensed rule is represented as:
F = C – P + 1

8. The Line joining a liquid phase with liquid and solid phase mixture is known as ____________
a) Liquidus
b) Solidus
c) Tie line
d) Solvus

Explanation: Liquidus is the line joining liquid phase with liquid and solid phase mixture.

9. The line joining a solid phase with liquid and solid phase mixture is known as _____________
a) Liquidus
b) Solidus
c) Tie line
d) Solvus

Explanation: Solidus is the line joining liquid phase with liquid and solid phase mixture.

10. Melting point of copper (in oC) is?
a) 985
b) 1085
c) 1453
d) 1200

Explanation: The copper has a melting point of 1085oC.

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