250+ TOP MCQs on P-Block Elements – Sulphur – Allotropic Forms and Answers

Chemistry Multiple Choice Questions on “P-Block Elements – Sulphur – Allotropic Forms”.

1. What is the chemical structure and formula of sulfur?
a) S₈, S
b) S, S₈
c) S, S
d) S₈, S₈
Answer: a
Clarification: The chemical formula of elemental sulfur is S, as represented in the periodic table. However, in structural aspects, a molecule of sulfur comprises of 8 sulfur atoms, bond together to form S₈.

2. Which characteristic of crude petroleum is a consequence of sulfur?
a) Acidity
b) Sourness
c) Alkalinity
d) Foul odor
Answer: b
Clarification: Sourness of crude petroleum is a main characteristic caused by the presence of sulfur. Usually, crude petroleum is termed to be sweet if concentration of sulfur is less than 0.5%. If it is more, then it is termed as sour crude.

3. What is the transition temperature of alpha- and beta-sulfur?
a) 369 °C
b) 369 °F
c) 95.9 °C
d) 95.9 °F
Answer: c
Clarification: Transition temperature is where both dominant forms of sulfur, alpha and beta are stable. For sulfur, the transition temperature is 369K (or 95.9°C), below which alpha-sulfur is most stable and above which, beta sulfur is most stable.

4. Which is a more vital source of elemental sulfur?
a) Oceans
b) Wind
c) Soil
d) Volcanoes
Answer: d
Clarification: Elemental sulfur is predominantly found near volcanic craters. This is because the sulfur dioxide released from the craters condenses to form liquid sulfur. This then solidifies to form elemental sulfur. In soil and oceans, sulfur is usually found in the form of pyrites.

5. What are pyrites known as fool’s good?
a) Because of sulfides
b) Because of lead
c) Because of carbonates
d) Because of iron
Answer: a
Clarification: Pyrite is the general name for the mineral ore of sulfur. Two commonly known pyrites are iron-pyrite, FeS₂ and copper pyrite, CuFeS₂. They are often termed as fool’s gold because of the mineral’s metallic-brass like luster which closely resembles gold metal.

6. When a flask containing sodium thiosulfate is placed over a paper marked with ‘X’ and HCl added to it, the ‘X’ seems to disappear when looked through the flask. Why?
a) Because of formation of sodium chloride
b) Because of sulfur precipitating
c) Because of release of yellowish chlorine gas
d) Because of dissolution of sulfur
Answer: b
Clarification: When sodium thiosulfate is treated with hydrochloric acid, sodium chloride is formed along with elemental sulfur. This yellow sulfur precipitates and causes the mark ‘X’ to fade away.

7. Which of the following is used for vulcanization purposes in the rubber industry?
a) Sulfuric acid
b) Sulfur dioxide
c) Sulfur
d) Sulfur trioxide
Answer: c
Clarification: Sulfur is the prime vulcanizing agent in rubber and tire industry. Vulcanizing agents are used to form extensive cross links in natural polymers to increase their strength, durability, elasticity. It is usually added to tire rubber and heated to form cross polymer linkages.

8. What is the name of the process of extracting sulfur on commercial scale?
a) Bosch process
b) Boyle process
c) Ostwald process
d) Frasch process
Answer: d
Clarification: Frasch process is the industrial grade process of mining elemental sulfur from underground deposits. This is done by using pipelines and pumping superheated water and causing the molten sulfur to rise up which is then solidified. It was invented in 1894.

9. What is the oxidation number of sulfur in dithionous acid?
a) -3
b) +3
c) +6
d) -6
Answer: b
Clarification: Dithionous acid is formulated as H₂S₂O₄. Since H can acquire ON of +1 and O of -2 each, then assuming ON of S to be X,
(2 x +1) + (2 x X) + (4 x -2) = 0
On solving, X = +3
The oxidation state/number of sulfur in dithionous acid is +3.

10. What is the common name of O₂SCl₂?
a) Sulfur oxochloride
b) Sulfuryl dioxo-dichloride
c) Sulfuryl chloride
d) Thionyl chloride
Answer: c
Clarification: The common name of SO₂Cl₂ is sulfuryl chloride. Usually, it is confused with thionyl chloride. It is an inorganic, colorless liquid with highly pungent odor. It can only be synthesized in labs and not found in nature.

11. Who first recognized sulfur as an element?
a) John Dalton
b) Humphry Davy
c) Louis Pasteur
d) Antoine Lavoisier
Answer: d
Clarification: In ancient times, sulfur was thought to be fused with mercury and salt towards which alchemists thought it was a metal that could be transmuted. It was Antoine Lavoisier who first thought sulfur was an element. However, Humphry Davy believed it contained hydrogen.

12. What percentage of Earth’s mass is sulfur?
a) 3%
b) 5%
c) 0.032%
d) 2%
Answer: a
Clarification: Factually, 3% of Earth’s total mass is comprised of elemental sulfur. Carbon makes u about 0.032% of Earth’s crust and outer mantle. On the other hand, iron and magnesium account for 5% and 2% of Earth’s crust, respectively.