Corrosion Engineering Multiple Choice Questions on “Mineral Acids – Sulfuric Acid”.
1. Which of the following is/are the examples of mineral acids?
a) Sulfuric acid and nitric acid
b) Hydrochloric acid and hydrofluoric acid
c) Sulfuric, nitric, hydrochloric, hydrofluoric and phosphoric acid
d) Sulfuric, nitric, hydrochloric and hydrofluoric acid
Answer: c
Clarification: Mineral acid or inorganic acid is the acid derives from one or more inorganic compounds on dissolution with water. This includes sulfuric acid, nitric acid, hydrochloric acid, hydrofluoric acid, and phosphoric acid.
2. Which of the following acid is produced relatively higher than other acids?
a) Nitric acid
b) Sulfuric acid
c) Phosphoric acid
d) Hydrofluoric acid
Answer: b
Clarification: Sulfuric acid is produced relatively higher than other acids. The chemical formula for sulfuric acid is H2SO4. It is produced by absorbing water into oleum.
3. What are the principal uses of sulfuric acid?
a) Production of hydrochloric acid
b) Manufacturing of dyes, fertilizers, and drugs
c) Pickling of steels and other metals
d) Production of hydrochloric acid, manufacturing of dyes, fertilizers and drugs and pickling of steels
Answer: d
Clarification: Principle uses of sulfuric acid are:
- Production of hydrochloric acid and other chemicals
- Manufacturing of dyes, fertilizers, drugs, explosives, and rayon
- Pickling of steels and other metals
- Laboratory usage.
4. Which of the following method is used to produce sulfuric acid?
a) Contact process
b) Ostwald process
c) Solvay process
d) Haber process
Answer: a
Clarification: Sulfuric acid is produced by the contact process or leads chamber process. It is produced by absorbing SO3 with water. This process accounts for 70% of world production.
5. Which of the following statements is/are true regarding the contact process?
a) Conversion of sulfur dioxide to sulfur trioxide takes place
b) Vanadium oxide is used as a catalyst
c) It accounts for 70% of the world’s production
d) Conversion of sulfur dioxide to sulfur trioxide takes place in the presence of vanadium catalyst and it accounts for 70% world’s production
Answer: d
Clarification: Contact process:
- Sulfur compounds such as copper sulfide are burned to get SO2
- Catalytic conversion of sulfur dioxide to sulfur trioxide takes place
- Absorption of SO3 into water produces sulfuric acid.
6. Which of the following concentration of sulfuric acid in which the corrosion rate of steel is minimum?
a) Less than 30%
b) Greater than 70%
c) 30% – 70%
d) above 110%
Answer: b
Clarification: Ordinary steels are widely used for various concentrations of sulfuric acid greater than 70% purity. Dilute acids attack steel very rapidly and result in faster degradation.
7. Which of the following is/are the factors that affect the corrosion resistance of steel in concentrated sulfuric acid?
a) High velocity
b) Temperature of acid
c) Aeration
d) High velocity, temperature, and aeration
Answer: d
Clarification: High velocity, the temperature of acid and aeration are the factors that affect the corrosion resistance of steel in concentrated sulfuric acid (>70%).
8. Which of the following metal is not corrosion resistant to sulfuric acid?
a) Grey cast iron
b) Duriron
c) Durimet 20
d) Lead
Answer: a
Clarification: Grey cast iron is not corrosion resistant to sulfuric acid as it penetrates the metal along with the graphite flakes. Though the corrosion rates are small but the metal may split open in service.
9. Lead is used extensively for sulfuric acid in the lower concentration ranges (<70%).
a) False
b) True
Answer: b
Clarification: Lead is used extensively for sulfuric acid in the lower concentration ranges (<70%). It is not recommended above 70% purity is due to the solubility of lead sulfate surface film in the acid.
10. Which of the following is/are the applications of Duriron because of its corrosion resistance and inherent hardness?
a) To manufacture pumps, valves, and fans
b) To make heat exchangers
c) Impressed–current anodes
d) To manufacture pumps, valves, fans, heat exchangers and impressed-current anodes
Answer: d
Clarification: Duriron is high-silicon cast iron with high corrosion resistance and inherent hardness. It is used to manufacture pumps, valves, fans, heat exchangers, and impressed-current anodes.
11. Which of the following alloying elements are not recommended in the sulfuric acid environment?
a) Chromium
b) Nickel
c) Molybdenum
d) Nickel and molybdenum
Answer: c
Clarification: Alloying elements are added in base metal to exhibit certain specific properties such as corrosion resistance, thermal properties, or mechanical properties. Here molybdenum is not recommended as an alloying element in high-silicon cast iron for sulfuric acid application.