Chemistry MCQs
Chemistry Objective (Multiple Choice) General Knowledge Questions & Answers for SSC-CGL, UPPSC, UPSC, NDA, CDS and UPSC Civil Services Prelims Examination.
1. When Sulphur is heated with rubber, the process is commonly known as ?
[A] Galvanization
[B] Sulphonation
[C] Vulcanization
[D] Hydrodesulfurization
Show Answer
Correct Answer: C [Vulcanization]
Notes:
Natural rubber becomes soft at high temperature (>335 K) and brittle at low temperatures (<283 k) and shows high water absorption capacity. It is soluble in non-polar solvents and is non-resistant to attack by oxidising agents. To improve upon these physical properties, a process of vulcanisation is carried out. This process consists of heating a mixture of raw rubber with sulphur and an appropriate additive at a temperature range between 373 K to 415 K. On vulcanisation, sulphur forms cross links at the reactive sites of double bonds and thus the rubber gets stiffened.
In the manufacture of tyre rubber, 5% of sulphur is used as a crosslinking agent
2. What is commonly referred to as “Laughing Gas”?
[A] Nitric oxide
[B] Nitrous oxide
[C] Nitrogen penta oxide
[D] Nitrogen
Show Answer
Correct Answer: B [Nitrous oxide]
Notes:
Nitrous oxide is often referred to as “Laughing Gas” due to the euphoric effect it produces when inhaled. Its chemical formula is N2O and it is an oxide of nitrogen. At room temperature, it is a colorless, non-flammable gas with a relatively sweet odor and taste. It is primarily used in dentistry and surgery for its analgesic and anesthetic properties. It is also noted for its role as a major greenhouse gas and air pollutant, as well as a natural regulator of stratospheric ozone.
3. Galena & Litharge are ores of which of the following metals?
[A] Mercury
[B] Zinc
[C] Copper
[D] Lead
Show Answer
Correct Answer: D [Lead]
Notes:
Galena and litharge are ores of lead. Galena is the most common ore of lead. It is the natural mineral form of lead (II) sulphid. Litharge is a secondary mineral that forms from the oxidation of galena ores. It is one of the natural mineral forms of Lead(II) oxide.
4. What is the primary use of Phenolphthalein in chemistry?
[A] A Solvent
[B] A Dye
[C] A Catalyst
[D] A Detergent
Show Answer
Correct Answer: B [A Dye]
Notes:
Phenolphthalein is commonly employed as a pH indicator in titrations due to its distinct color change in varying pH levels. At pH 8.2, it appears colorless but turns pink as the pH increases to 10. It is not used as a solvent, catalyst or detergent. It also finds applications in forensic science for detecting latent blood stains.
5. Which of the following processes commonly use the method of adsorption?
[A] Scrubbers manufacturing
[B] Purification of solid substances
[C] Chromatography
[D] Purification of liquid substances
Show Answer
Correct Answer: C [Chromatography]
Notes:
Adsorption, the binding of gas or liquid particles to a solid surface, is often used in chromatography – a laboratory technique for the separation of a mixture. This process is critical as it allows the separation of the compounds in the mixture, thereby enabling further analysis or purification. Apart from chromatography, adsorption is also used in scrubbers and purification of solids and liquids.
6. The primary part of Liquefied Petroleum Gas LPG is ______?
[A] Butane
[B] Methane
[C] Propane
[D] Butane or Propane
Show Answer
Correct Answer: D [Butane or Propane]
Notes:
LPG consists mainly of propane, propylene, butane, and butylene in various mixtures. The primary gas can be either Propane or Butane.
7. Which of the following elements is the most electronegative?
[A] Chlorine
[B] Fluorine
[C] Bromine
[D] All of them have the same electronegativity
Show Answer
Correct Answer: B [Fluorine]
Notes:
Electronegativity is defined as an atom’s ability to attract an electron pair when forming a covalent bond. This property increases as you move left to right across the periodic table due to an increase in the nuclear charge’s attractive forces. It decreases as you move top to bottom, owing to the shielding effect of sub-levels and increased atomic radius, which makes electrons easier to remove. This culminates in Fluorine, being the highest and furthest to the right on the periodic table, hence it is the most electronegative.
8. Which among the following is Fool’s Gold?
[A] Copper Sulphate
[B] Iron Sulfide
[C] Brass
[D] Silver Bromide
Show Answer
Correct Answer: B [Iron Sulfide]
Notes:
The mineral pyrite or iron pyrite, also known as fool’s gold, is an iron sulfide with the chemical formula FeS2 (iron (II) disulfide). “Fool’s Gold” is technically known as pyrite or iron sulfide (FeS2) and is one of the most common sulfide minerals. Its nickname is “Fool’s Gold,” but it often contains a surprising amount of gold.
9. Which among the following makes Chile saltpetre different from saltpetre?
[A] Nitrate
[B] Sodium
[C] Magnesium
[D] Calcium
Show Answer
Correct Answer: B [Sodium]
Notes:
Chile saltpetre, or sodium nitrate (NaNO3), differs from regular saltpetre, which typically refers to potassium nitrate (KNO3). Chile saltpetre is primarily composed of sodium, while traditional saltpetre contains potassium. Historically, Chile saltpetre was extensively mined in the Atacama Desert and was crucial for fertilizer and explosives in the 19th century.
10. Amalgam’ is a term used for an alloy of a metal with :
[A] Copper
[B] Mercury
[C] Lead
[D] Aluminium
Show Answer
Correct Answer: B [Mercury]
Notes:
The correct answer is Mercury. An amalgam is a specific type of alloy that primarily consists of mercury mixed with another metal, commonly used in dental fillings due to its durability and ease of use. Historically, amalgams have been used since ancient times, with the earliest known use dating back to the 9th century in China.