BPSC PGT Chemistry: p-Block Elements Important Compounds of Carbon and Silicon

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1. What is the full form of LPG?
a) liquefied phenolic gas
b) liquefied pentane gas
c) liquefied petroleum gas
d) liquid petroleum gas

Answer: c
Explanation: LPG stands for Liquefied Petroleum Gas, which mainly contains n-butane and isobutane. It is widely used as a domestic fuel and is commonly employed in households for cooking purposes.

2. Which of the following mixtures is known as producer gas?
a) carbon dioxide and hydrogen
b) carbon monoxide and hydrogen
c) carbon monoxide and nitrogen
d) carbon dioxide and nitrogen

Answer: c
Explanation: When carbon reacts at around 1273 K, it doesn’t just stay quiet — it teams up with oxygen and nitrogen to create a special fuel mixture called producer gas (mainly carbon monoxide and nitrogen). On the other hand, when carbon monoxide unites with hydrogen, the result is another important fuel mixture known as water gas.

3. Which of the following is not a property of carbon monoxide?
a) odourless
b) colourless
c) water-insoluble
d) oxidising agent

Answer: d
Explanation: Carbon monoxide is a sneaky gas — you can’t see it, you can’t smell it, and it barely dissolves in water. Yet, despite being invisible and odourless, it’s incredibly powerful as a reducing agent. In fact, this gas plays a key role in metallurgy, helping extract metals like iron (from ferrous oxide) and zinc (from zinc oxide) by reducing their oxides to pure metal.

4. The cross-linked polymer compounds containing silicone which are linear and the cyclic are called ___________
a) coal
b) silicones
c) silicate
d) silicanes

Answer: b
Explanation: Silicones are polymers that may be linear, cyclic, or cross-linked and contain R₂SiO as their repeating unit. They are produced from alkyl-substituted chlorosilanes and are well-known for being chemically inert, water-repellent, and resistant to heat.

5. Carbon dioxide forms carbonic acid with water.
a) true
b) false

Answer: a
Explanation: Carbon dioxide, represented as CO₂, is a colourless and odourless gas. When it dissolves in water, it doesn’t stay idle — it reacts to form carbonic acid (H₂CO₃). This weak acid further breaks down in water, giving rise to bicarbonate (HCO₃⁻) and hydronium (H₃O⁺) ions, as shown in the balanced equation:

H₂CO₃(aq) + H₂O → HCO₃⁻ + H₃O⁺

6. What is the chemical formula of beryl?
a) Be₃Al₂Si₆O₁₈
b) Be₃AlSi₆O₁₈
c) Be₃Al₂Si₆O
d) BeAl₂Si₆O₁₈

Answer: a
Explanation: Beryl has the chemical formula Be₃Al₂Si₆O₁₈. It belongs to the group of cyclic silicates, where two oxygen atoms are shared. Its fundamental structural unit is Si₆O₁₈¹²⁻, and it is commonly called beryllium aluminium cyclosilicate.

7. When aluminium ions replace silicon ions and silicon dioxide what is it called?
a) silicanes
b) silicates
c) silicons
d) zeolites

Answer: d
Explanation: When some aluminium ions replace silicon ions in the three-dimensional network of silicon dioxide, the resulting structure is called an aluminosilicate. To balance the negative charge, cations such as sodium, potassium, or calcium are required. Common examples include zeolites and feldspar.

8. Talcum powder has a slippery touch.
a) True
b) False

Answer: a
Explanation: Talc is made up of flat sheets that can easily slide over each other because of weak attractive forces. This property makes talc the main ingredient of talcum powder, giving it a smooth and slippery feel. Hence, the statement is true.

9. What is the second hardest material known?
a) Coke
b) Carborundum
c) Graphite
d) Diamond

Answer: b
Explanation: Carborundum is the second hardest material known and has a formula of silicon carbide that is SiC. It is used as a semiconductor at high-temperature and also in transistor diode rectifiers. Diamond is the first hardest material known.

10. Which of the following is not a component of glass?
a) Sodium chloride
b) Calcium carbonate
c) Silica
d) Sodium carbonate

Answer: a
Explanation: Glass is a transparent or translucent amorphous substance, which is obtained by fusion of sodium carbonate or sodium sulphate, calcium carbonate and sand (which is also known as silica), the general formula of glass is Na₂O.CaO.6SiO₂

11. which of the following is not a part of the composition of natural gas?
a) hydrocarbons
b) methane
c) ethane
d) benzene

Answer: d
Explanation: Natural gas occurs underground along with petroleum and mainly consists of methane, with smaller amounts of ethane, propane, and higher hydrocarbons. It is widely used as a fuel, and its combustion produces carbon black, which serves as a reinforcing material in rubber.

12. What is the basic structural unit of a silicate?
a) Si₄^–
b) SiO^–
c) SiO₄
d) SiO₄^4-

Answer: d
Explanation: Silicates are basically metal salts of silicic acid (H₂SiO₃). They are usually made by fusing metal oxides or carbonates with sand. At their core, all silicates are built from the same fundamental block — the silicate ion (SiO₄⁴⁻). A common example of this family is Zircon (ZrSiO₄), a well-known silicate mineral.

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