Chemistry MCQs
Chemistry Objective (Multiple Choice) General Knowledge Questions & Answers for SSC-CGL, UPPSC, UPSC, NDA, CDS and UPSC Civil Services Prelims Examination.
1. Dalton’s name is associated with which of the following terms?
[A] Electron
[B] Proton
[C] Atom
[D] Neutron
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Correct Answer: C [Atom]
Notes:
John Dalton introduced the atomic theory into chemistry. The main points of Dalton’s atomic theory are (1) Elements are made of extremely small particles called atoms. (2) Atoms of a given element are identical in size, mass and other properties; atoms of different elements differ in size, mass and other properties.(3) Atoms cannot be subdivided, created or destroyed. (4) Atoms of different elements combine in simple whole-number ratios to form chemical compounds. (5) In chemical reactions, atoms are combined, separated or rearranged.
2. Which among the following methods can be used to remove the permanent hardness in water due to calcium or magnesium sulphates?
[A] Sulphonate method
[B] Nitrate method
[C] Zeolite method
[D] None of these
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Correct Answer: C [Zeolite method ]
Notes:
Zeolite is hydrated Sodium Alumino-silicate capable of exchanging reversible Sodium ions for hardness producing ions in water. It is also use as softening of water. It is used to remove the permanent hardness in water due to Calcium or Magnesium sulphates.
3. Galena & Litharge are ores of which of the following metals?
[A] Mercury
[B] Zinc
[C] Copper
[D] Lead
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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 happens to water’s vapor pressure when heated?
[A] It increases
[B] It decreases
[C] It first increases then decreases
[D] No change
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Correct Answer: A [It increases]
Notes:
Vapor pressure of water increases as its temperature rises. At 25°C, water’s vapor pressure is approximately 23.8 mmHg, while at 100°C it reaches 760 mmHg. When a liquid is heated, kinetic energy of molecules grows, allowing more to escape as vapor and thus increasing vapor pressure.
5. Which among the following is the main constituent of vegetable oil and animal fats?
[A] Glycogen
[B] Triglyceride
[C] Galactose
[D] Diglyceride
Show Answer
Correct Answer: B [Triglyceride]
Notes:
The main constituent of vegetable oil and animal fats is triglyceride. Triglycerides are composed of three fatty acids linked to a glycerol molecule. They are the most common type of fat found in the body and serve as a major energy source. In fact, triglycerides account for about 95% of the fats in the human diet.
6. Which among the following is produced when we pass chlorine into slaked lime?
[A] DDT
[B] Baking Powder
[C] Bleaching Powder
[D] Gypsum
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Correct Answer: C [ Bleaching Powder]
Notes:
Bleaching powder is made by passing Cl2 into slaked lime. Though bleaching powder is often written as Ca(OCl)2 , it is really a mixture and not a compound.
7. Which of the following is correct about tincture of iodine?
[A] It is a solution of iodine in ethanol
[B] It is a solution of iodine in Hydrochloric acid
[C] It is a solution of iodine in Nitric acid
[D] None of the above
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Correct Answer: A [It is a solution of iodine in ethanol]
Notes:
A solution of iodine in alcohol known as ‘tincture of iodine’, has iodine (solid) as the solute and alcohol (liquid) as the solvent.
8. What do we call the region of space around the nucleus where the probability of finding an electron is maximum?
[A] Shell
[B] sub-shell
[C] Orbital
[D] electron cloud
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Correct Answer: C [Orbital]
Notes:
The region of space around the nucleus where the probability of finding an electron is maximum is called an orbital. The electron cloud is a visual model that represents all the orbitals in an atom
9. Which of the following reactions represents changing of green colour of ferrous sulphate?
[A] Double Displacement reaction
[B] Displacement reaction
[C] Combination reaction
[D] Decomposition reaction
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Correct Answer: D [Decomposition reaction]
Notes:
A reaction in which a single reactant breaks down to give simpler products is known as decomposition reaction. Ferrous sulphate crystals lose water when heated and the colour of the crystals changes. It then decomposes to ferric oxide, sulphur dioxide and sulphur trioxide.
10. Which of the following reactions take place when iron nail in a copper sulphate solution becomes brownish in colour?
[A] Decomposition reaction
[B] Displacement reaction
[C] Double Displacement reaction
[D] None of the above
Show Answer
Correct Answer: B [Displacement reaction]
Notes:
Iron nail in the Copper Sulphate solution become brownish in colour and the blue colour of copper sulphate solution fade. This happens because iron has displaced or removed another element, copper, from copper sulphate solution. This reaction is known as displacement reaction.