This set of Powder Metallurgy Multiple Choice Questions & Answers (MCQs) focuses on “Classes of Reactions and Physicochemical Mechanism ”.
1. ______ different types of reactions are possible in SHS.
a) 6
b) 7
c) 8
d) 5
View Answer
Explanation: The six different types of reactions possible in SHS are: (1) Synthesis from elements, (2) Redox reaction, (3) Oxidation of metals with complex oxides, (4) Synthesis from compounds, (5) Reaction of the elements with decomposition products and (6) Thermal decomposition.
2. Which of the following equation represents ‘Synthesis from elements’ type of SHS reaction?
a) Ti + C → TiC
b) B2O3 + 3Mg + N2 → 2BN + 3MgO
c) Nb + Li2O2 + 0.5Ni2O5 → 2LiNbO3
d) PbO + WO3 → PbWO4
View Answer
Explanation: Ti + C → TiC represents synthesis from elements type of SHS reaction; B2O3 + 3Mg + N2 → 2BN + 3MgO represents redox reaction; Nb + Li2O2 + 0.5Ni2O5→ 2LiNbO3 represents oxidation of metals with complex oxides type of SHS reaction while PbO + WO3 → PbWO4 represents synthesis from compounds type of SHS reaction.
3. Which of the following equation represents ‘oxidation of metals with complex oxides’ type of SHS reaction?
a) PbO + WO3 → PbWO4
b) B2O3 + 3Mg + N2 → 2BN + 3MgO
c) Ni + Al → NiAl
d) Nb + Li2O2 + 0.5Ni2O5 → 2LiNbO3
View Answer
Explanation: Ni + Al → NiAl represents synthesis from elements type of SHS reaction; B2O3 + 3Mg + N2 → 2BN + 3MgO represents redox reaction; Nb + Li2O2 + 0.5Ni2O5 → 2LiNbO3 represents oxidation of metals with complex oxides type of SHS reaction while PbO + WO3 → PbWO4 represents synthesis from compounds type of SHS reaction.
4. Which of the following equation represents ‘Redox reaction’ type of SHS reaction?
a) Ti + C → TiC
b) B2O3 + 3Mg + N2 → 2BN + 3MgO
c) Nb + Li2O2 + 0.5Ni2O5 → 2LiNbO3
d) 2TiH2 + N2 → 2TiN + 2H2
View Answer
Explanation: Ti + C → TiC represents synthesis from elements type of SHS reaction; B2O3 + 3Mg + N2 → 2BN + 3MgO represents redox reaction; Nb + Li2O2 + 0.5Ni2O5 → 2LiNbO3 represents oxidation of metals with complex oxides type of SHS reaction while 2TiH2 + N2 → 2TiN + 2H2 represents reaction of the elements with decomposition products type of SHS reaction.
5. Which of the following equation represents ‘Thermal decomposition’ type of SHS reaction?
a) Nb + Li2O2 + 0.5Ni2O5 → 2LiNbO3
b) 2TiH2 + N2 → 2TiN + 2H2
c) 2BH3N2H4 → 2BN + N2 + 7H2
d) B2O3 + 3Mg + N2 → 2BN + 3MgO
View Answer
Explanation: 2BH3N2H4 → 2BN + N2 + 7H2 represents thermal decomposition type of SHS reaction; Nb + Li2O2 + 0.5Ni2O5 → 2LiNbO3 represents oxidation of metals with complex oxides type of SHS reaction; 2TiH2 + N2 → 2TiN + 2H2 represents reaction of the elements with decomposition products type of SHS reaction while B2O3 + 3Mg + N2 → 2BN + 3MgO represents redox reaction.
6. Which of the following equation represents ‘Synthesis from compounds’ type of SHS reaction?
a) PbO + WO3 → PbWO4
b) B2O3 + 3Mg + N2 → 2BN + 3MgO
c) Nb + Li2O2 + 0.5Ni2O5 → 2LiNbO3
d) Ni + Al → NiAl
View Answer
Explanation: PbO + WO3 → PbWO4 represents synthesis from compound type of SHS reaction; B2O3 + 3Mg + N2 → 2BN + 3MgO represents redox reaction; Nb + Li2O2 +0.5Ni2O5 → 2LiNbO3 represents oxidation of metals with complex oxides type of SHS reaction while Ni + Al → NiAl represents synthesis from element type of SHS reaction.
7. Which of the following equation represents ‘reaction of the elements with decomposition products’ type of SHS reaction?
a) Ni + Al → NiAl
b) 2TiH2 + N2 → 2TiN + 2H2
c) B2O3 + TiO2 + 5Mg → TiB2 + 5MgO
d) 2BH3N2H4 → 2BN + N2 + 7H2
View Answer
Explanation: 2TiH2 + N2 → 2TiN + 2H2 represents reaction of the elements with decomposition products type of SHS reaction; Ni + Al → NiAl represents synthesis from element; B2O3 + TiO2 + 5Mg → TiB2 + 5MgO represents redox reaction; and 2BH3N2H4 → 2BN + N2 + 7H2 represents thermal decomposition type of SHS reaction.
8. In SHS reactions, an important parameter is the _________
a) Isothermal temperature
b) Volumetric expansion
c) Adiabatic temperature
d) Heat
View Answer
Explanation: In SHS reactions, an important parameter is the adiabatic temperature, Tad. This refers to the temperature to which the products are raised under adiabatic conditions due to the heat evolved during the chemical reaction. If this temperature is less than the boiling point of both the constituents, no vapor phase is formed.
9. In the case of TiB2, high pressures are needed to make it a gasless combustion.
a) True
b) False
View Answer
Explanation: In case of TiB2, though the adiabatic temperature is less than the boiling point of Ti and B, the vapor pressure of the elements at the adiabatic temperature is high, and hence high pressures are needed to make it a gasless combustion.
10. Solid state combustion leads to _______ combustion velocities.
a) Highest
b) Lowest
c) Lower
d) High
View Answer
Explanation: Solid state combustion is the combustion process where all components are in a solid state. It occurs entirely when the melting points of the constituents are less than the adiabatic temperature leading to the lowest combustion velocities.
11. For which of the following conditions does the combustion proceeds at the highest velocity (where MPC1 and MPC2 are melting points of component 1 and 2 respectively)?
a) MPC1 < Tad < MPC2
b) Tad > MPC1 and MPC2
c) Tad < MPC1 and MPC2
d) Tad = MPC1 and MPC2
View Answer
Explanation: If the adiabatic temperature lies in between the melting point of the components, the molten component spreads at a high rate in the compact, and the combustion proceeds at the highest possible speed.
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