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. 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.
3. Which among the following of a catalyst does not change at the end of a reaction?
[A] Quantity
[B] Chemical Composition
[C] Both Quantity and Chemical com position
[D] None of the above
Show Answer
Correct Answer: C [Both Quantity and Chemical com position]
Notes:
A catalyst is a substance that increases the rate of a chemical reaction without undergoing any permanent change itself. At the end of the reaction, a catalyst retains its original quantity and chemical composition. This property allows it to be used repeatedly in reactions. For example, enzymes, which are biological catalysts, remain unchanged after facilitating biochemical reactions.
4. The synthetic rubber Buna is obtained from the reaction of an unsaturated hydrocarbon with ___:
[A] Sodium
[B] Magnesium
[C] Potassium
[D] Lithium
Show Answer
Correct Answer: A [Sodium]
Notes:
Buna-S is a synthetic rubber formed by co-polymerization of a mixture of 1:3 butadiene and styrene. It is obtained from Sodium.
5. Which of the following alkali metal ions has the highest hydration enthalpy?
[A] Lithium
[B] Sodium
[C] Potassium
[D] Caesium
Show Answer
Correct Answer: A [Lithium]
Notes:
Lithium ions has maximum degree of hydration and for this reason lithium salts are mostly hydrated.
6. Which of these compounds is also known as wood spirit?
[A] Ethanol
[B] Methanol
[C] Propanol
[D] None of the above
Show Answer
Correct Answer: B [Methanol]
Notes:
Methanol, CH3OH, also known as ‘wood spirit’. It was produced by destructive distillation of wood.
7. Which of the following is correct about ozone?
[A] it is a red coloured gas
[B] it is odourless
[C] it is harmless in small concentrations
[D] All of the above
Show Answer
Correct Answer: C [it is harmless in small concentrations]
Notes:
Pure ozone is a pale blue gas, dark blue liquid and violet-black solid. Ozone has a characteristic smell and in small concentrations it is harmless. However, if the concentration rises above about 100 parts per million, breathing becomes uncomfortable resulting in headache and nausea.
8. What do we call the compounds having identical molecular formula but different structures?
[A] Functional isomers
[B] Structural isomers
[C] Mirror isomers
[D] Branched isomers
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Correct Answer: B [Structural isomers]
Notes:
The compounds with identical molecular formula but different structures are called structural isomers.
9. What is Tyndall effect?
[A] scattering of a beam of light by the particles of a suspension
[B] refraction of a beam of light by the particles of a solution
[C] scattering of a beam of light by the particles of a colloid
[D] reflection of a beam of light by the particles of a suspension
Show Answer
Correct Answer: C [scattering of a beam of light by the particles of a colloid]
Notes:
The scattering of a beam of light by the particles of a colloid is called the Tyndall effect.
10. Which of the following alpha-emitter is commonly used in smoke detectors?
[A] Bismuth – 209
[B] Amrecium-231
[C] Uranium-238
[D] Protactinium-231
Show Answer
Correct Answer: B [Amrecium-231]
Notes:
Americium-241 is an isotope of americium. It is the most common isotope of americium having a half-life of 432.2 years. It is radioactive and is commonly used in ionization type smoke detectors.
