Corrosion Engineering Multiple Choice Questions on “Modern Theory Principles – Thermodynamics – 1”.
1. Which of the following is/are the applications of modern electrode kinetic principles?
a) Anodic protection
b) Noble metal alloying
c) Methods to measure corrosion rates rapidly
d) Anodic protection, noble metal alloying and methods to measure corrosion rates rapidly
Answer: d
Clarification: Modern electrode kinetics deals with electrochemical corrosion of aqueous solution and it results in the applications of
2. What is the direct measure of work capacity or electrical energy available from a system?
a) Change in enthalpy
b) Change in Gibbs free energy
c) Reaction time
d) Concentration of reactants
Answer: b
Clarification: Change is Gibbs free energy is the difference of free energies of the reaction products and reactants. And it is a direct measure of the work capacity or maximum electrical energy available in from a system.
3. If the transition of a system from one state to another state resulted in negative free energy change then it is known as a spontaneous reaction.
a) True
b) False
Answer: a
Clarification: If the transition of a system from one state to another state resulted in negative free energy change then it is known as a spontaneous reaction. It means the free energy of products is less than the free energy of reactants.
4. Which of the following is true, if the transition of a system results in positive Gibbs free energy change?
a) It is a spontaneous reaction
b) Free energy of products is less
c) It is a non-spontaneous reaction
d) Free energy of reactants is more
Answer: c
Clarification: If the transition of a system from one state to another state resulted in positive free energy change then it is known as a non-spontaneous reaction. It means the free energy of reactants is less than the free energy of products. It requires external heat or force to proceeds with the reaction.
5. Which of the following is a spontaneous reaction?
a) Production of ammonia
b) Corrosion of metals
c) Photosynthesis reaction
d) Generation of oxygen from water
Answer: b
Clarification: Spontaneous reaction is a reaction in which the reactants convert into products without any supply of external energy. Oxidation of metal atoms into metal ions due to the instability of metallic atoms is known as the corrosion of metals.
6. The change in Gibbs free energy is a path function and it is independent of the state of the system.
a) False
b) True
Answer: a
Clarification: The change in Gibbs free energy is a state function and it is independent of the path followed by the system to reach that state. It is denoted by ΔG (delta G).
7. Which of the following formula is used to calculate the Gibbs free energy of an electrochemical reaction?
a) ΔG=-nFE0cell
b) ΔG=+nFE0cell
c) ΔG=-nFEcell
d) ΔG=+nFEcell
Answer: c
Clarification: ΔG=-nFEcell where n is the electrons participated in the reaction, F is the faraday constant (96500 coulombs), Ecell is the overall cell potential and E0cell is the standard cell potential.
8. What is the change in Gibb’s free energy of a Cu-Zn system with a cell potential of 1.10V?
a) -11.13 KJ/mol
b) +21.23 KJ/mol
c) +11.13 KJ/mol
d) -21.23 KJ/mol