General Science Chemistry MCQs
Chemistry Objective (Multiple Choice) General Knowledge Questions & Answers for SSC-CGL, UPPSC, UPSC, NDA, CDS and UPSC Civil Services Prelims Examination
51. Which of the following is emitted in Beta-decay process?
[A] Electron
[B] Positron
[C] Both a and b
[D] None
Show Answer
Correct Answer: C [Both a and b]
Notes:
In beta decay, a nucleus spontaneously emits an electron (βdecay) or a positron (β+decay). One can never predict which nucleus will undergo decay.
52. When is the gamma ray emitted?
[A] When a nucleus in a ground state goes to the excited state
[B] When a nucleus in an excited state spontaneously decays to its ground state
[C] When alpha rays and beta rays collide
[D] None of the above
Show Answer
Correct Answer: B [When a nucleus in an excited state spontaneously decays to its ground state]
Notes:
When a nucleus in an excited state spontaneously decays to its ground state (or to a lower energy state), a photon is emitted with energy equal to the difference in the two energy levels of the nucleus. This is the so-called gamma decay.
53. Which of the following substance was used as a moderator in CIRUS reactor?
[A] Heavy water
[B] water
[C] solid graphite
[D] No moderator was used
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Correct Answer: A [Heavy water]
Notes:
CIRUS (Canada India Research U.S.) reactor was constructed in 1960. This 40 MW reactor used natural uranium as fuel and heavy water as moderator.
54. Which of the following material is used to make control rods in a nuclear reactor?
[A] Indium
[B] Boron
[C] Cadmium
[D] All of the above
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Correct Answer: D [All of the above]
Notes:
The reaction rate is controlled through control-rods made out of neutron-absorbing materials. They are composed of chemical elements such as boron, silver, indium and cadmium that are capable of absorbing many neutrons without themselves fissioning.
55. Which of the following is an endothermic reaction?
[A] Decomposition of calcium carbonate to calcium oxide and carbon dioxide
[B] Respiration
[C] Burning of Natural gas
[D] All of the above
Show Answer
Correct Answer: A [Decomposition of calcium carbonate to calcium oxide and carbon dioxide]
Notes:
Decomposition of calcium carbonate to calcium oxide and carbon dioxide is an endothermic reaction. Respiration and Burning of Natural gas are examples of exothermic reactions.
56. Which of these methods can be used to prevent rancidity?
[A] Adding antioxidants to the food
[B] Storing food at low temperature
[C] Replace the air with nitrogen in the packing material
[D] All of the above
Show Answer
Correct Answer: D [All of the above]
Notes:
When food containing fats and oils are exposed to the atmosphere, the oxidation of fat and oil occurs, this is called as Rancidity.
57. Which of the following group of elements contain the noble gases?
[A] s-block
[B] p-block
[C] d-block
[D] f-block
Show Answer
Correct Answer: B [p-block]
Notes:
The p-Block Elements comprise those belonging to Group 13 to 18 and these together with the s-Block Elements are called the Representative Elements or Main Group Elements. The 18th group i.e. the last group of the p-block elements is the noble gases group.
58. Which is the first element in the Actinoid series?
[A] Actinium
[B] Bohrium
[C] Mendelevium
[D] Nobelium
Show Answer
Correct Answer: A [Actinium]
Notes:
The actinoid series comprises of the 15 metallic chemical elements with atomic numbers from 89 to 103 starting from actinium through lawrencium.
59. Choose the correct statement:
[A] Water exists as liquid due to hydrogen bonding
[B] Hydrogen bond is a weak bond as compared to ionic bond
[C] Both a and b
[D] None of the above
Show Answer
Correct Answer: C [Both a and b]
Notes:
Hydrogen bond is a weak bond and is quite small as compared to the covalent bond. it is due to hydrogen bonding only that water exists as a liquid.
60. Which of the following acids is produced by stomach in human body to help in digestion?
[A] Hydrochloric acid
[B] Sulphuric acid
[C] Nitric acid
[D] Benzoic acid
Show Answer
Correct Answer: A [Hydrochloric acid]
Notes:
Hydrochloric acid produced by the stomach in human body to help in digestion. During indigestion the stomach produces too much acid and this causes pain and irritation.
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