his set of Chemistry Multiple Choice Questions on “P-Block Elements – Oxoacids of Sulphur”.
1. What class of compounds do the oxygen based compounds of sulfur represent?
a) Acids
b) Bases
c) Neutral oxides
d) Amphoteric
Answer: a
Clarification: The oxygen compounds of sulfur represent the class of ‘oxoacids’ of sulfur. Generally, a non-metallic oxide is usually acidic in nature (given that exceptions like CO, N2O, NO). Examples include sulfurous acid (H2SO3), sulfuric acid (H2SO4) and many more.
2. Which of the following is the most popular oxoacid of sulfur?
a) Sulfurous acid
b) Sulfuric acid
c) Peroxodisulfuric acid
d) Pyrosulfuric acid
View Answer
Answer: b
Clarification: Sulfuric acid is commonly used in industrial chemical manufacturing as a reactant or a laboratory reagent. The formula is H2SO4. It is one of the most powerful oxidizing and dehydrating agents in the chemical field and finds a number of application, such as production of fertilizers and dyes and many more.
3. Which of the following is produced third in the contact process?
a) Sulfur dioxide
b) Sulfur trioxide
c) Pyrosulfuric acid
d) Sulfuric acid
Answer: c
Clarification: In the first step, sulfur is converted to sulfur dioxide. Second step involves reacting it with more oxygen to form sulfur trioxide. Instead of reacting sulfur trioxide with water to form sulfuric acid directly, an alternative, safer method is utilized to dissolve sulfur trioxide gas in sulfuric acid to form oleum, also known as pyrosulfuric acid.
4. Why is sulfur trioxide not dissolved in water and but treated with existing sulfuric acid?
a) It is not economically feasible
b) Manufacturing plants cannot withstand the great pressure of dissolving sulfur trioxide in water
c) Sulfur trioxide just hydrates on dissolving with no chemical bonds form
d) The heat of dissolution is very high and potentially dangerous
Answer: d
Clarification: The reaction between sulfur trioxide and water is highly exothermic and releases great amount of energy that no plant, currently, has the ability to withstand. Due to potential risks of explosion and fire hazard, sulfur trioxide is not dissolved in water but treated with sulfuric acid to produce oleum. This can be diluted to desired concentrations.
5. What is the primary product when carbon is treated with concentrated sulfuric acid?
a) Carbon dioxide
b) Carbon monoxide
c) Carbon sulfate
d) Carbon sulfide
Answer: a
Clarification: Since sulfuric acid is a very strong oxidant, it oxidizes carbon to carbon dioxide. With excess of oxygen available from sulfuric acid and water, carbon monoxide is rarely formed. Carbon sulfate does not exist and carbon sulfide formed as a reaction between carbon and sulfur.
6. What is the acidity of peroxodisulfuric acid?
a) 1
b) 3
c) 4
d) Does not exist
Answer: d
Clarification: Acids do not bear acidity. The number of hydrogen ions released by an acid is referred to as its basicity. The formula of peroxodisulfuric acid is H2S2O8 and can release 2 H+ ions, hence the acidity is 2.
7. What is the basicity of oleum?
a) 1
b) 7
c) 2
d) 3
Answer: c
Clarification: Basicity of acids refer to the number of H+ ions that can be released upon dissolution. In the case of oleum, which is also known as pyro sulfuric acid, the chemical formula being H2S2O7, the basicity is 2.
8. In the contact process, SO2 is passed twice through the catalytic converted. Why?
a) To produce less while converting to SO3
b) Since the energy and power consumed is less
c) To increase the yield
d) To avoid choking hazards