Chemistry MCQs
Chemistry Objective (Multiple Choice) General Knowledge Questions & Answers for SSC-CGL, UPPSC, UPSC, NDA, CDS and UPSC Civil Services Prelims Examination.
1. Which among the following element is an essential constituent of acids?
[A] Nitrogen
[B] Hydrogen
[C] Oxygen
[D] Helium
Show Answer
Correct Answer: B [Hydrogen]
Notes:
Acids are molecules that are able to donate proton or H+ thus, hydrogen is essential for acids. However, there are exception to this such as Bronsted acids. A Bronsted acid is an acid which can accept an electron pair, but does not have a proton (H+) to donate. Examples of such acids are Aluminum Chloride (AlCl3), Boron Trifuoride (BF3).
2. Which compound of mercury is used as antiseptic?
[A] Mercuric sulphide
[B] Mercuric oxide
[C] Mercuric chloride
[D] Mercuric iodide
Show Answer
Correct Answer: C [Mercuric chloride]
Notes:
Mercury chloride (HgCl2) is a highly toxic compound that volatizes slightly at ordinary temperature and appreciably at 100 degrees C. It is corrosive to mucous membranes and used as a topical antiseptic and disinfectant.
3. Which among the following is major component of Gobar Gas?
[A] Butane
[B] Ethane
[C] Propane
[D] Metahne
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Correct Answer: D [Metahne]
Notes:
Gobar Gas or Biogas is mostly methane (CH4) and carbon dioxide (CO2) and may have small amounts of hydrogen sulfide (H2S), moisture and siloxanes.
4. Which among the following makes Chile saltpetre different from saltpetre?
[A] Nitrate
[B] Sodium
[C] Magnesium
[D] Calcium
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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.
5. With reference to the Radioactivity, which among the following is called an isomeric transition?
[A] Alpha emission
[B] Gamma emission
[C] Beta emission
[D] X-Ray emission
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Correct Answer: B [ Gamma emission]
Notes:
An isomeric transition is a radioactive decay process that involves emission of a gamma ray from an atom where the nucleus is in an excited metastable state, referred to in its excited state, as a nuclear isomer. The emission of a gamma ray from an excited nuclear state allows the nucleus to lose energy and reach either a lower energy state, sometimes its ground state. In certain cases, the excited nuclear state following a nuclear reaction or other type of radioactive decay, has a half live that is more than 100 to 1000 times longer than the average 10-12 seconds, and this excited state is referred to as a metastable nuclear excited state. Some nuclei are able to stay in this metastable excited state for minutes, hours, days, or occasionally far longer, before undergoing gamma decay, in which they undergo radioactive decay with primary emission of a gamma ray.
6. The vegetable oil treated with which among the following halogens makes it an additive, which is used in artificial citrus flavoured aerated drinks to give it the cloudy look, so that consumers get deceived because it appears natural citrus drink?
[A] Chlorine
[B] Bromine
[C] Iodine
[D] Fluorine
Show Answer
Correct Answer: B [ Bromine]
Notes:
Brominated Vegetable Oil is an additive, which is used in artificial citrus flavoured aerated drinks to give it the cloudy look, so that consumers are fooled into believing that it is the real thing. India banned BVO in 1988. It is used in some countries.
7. Which of the following is the use of washing soda?
[A] softening of water
[B] manufacture of glass
[C] manufacture of paints
[D] All of the above
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Correct Answer: D [All of the above]
Notes:
It is used for softening of water, laundering, cleaning, manufacture of glass, soap, borax, paper, paints and textile It is also extensively used as laboratory reagent.
8. What is the general trend for ionization enthalpies of alkali metals as we move down the group?
[A] it increases
[B] it decreases
[C] it is same for all
[D] None
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Correct Answer: B [it decreases]
Notes:
The ionization enthalpies of the alkali metals are considerably low and decrease down the group from Li to Cs.
9. What is the hemihydrate of calcium sulphate commonly known as?
[A] Gypsum
[B] Plaster of Paris
[C] Chloroform
[D] Limestone
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Correct Answer: B [Plaster of Paris]
Notes:
Plaster of Paris is the common name of calcium sulphate hemihydrate because half molecule of water is attached with calcium sulphate. The chemical formula of plaster of Paris is CaSO4.1/2H2O.
10. Which of the following is the composition of vinegar?
[A] 65-75% solution of acetic acid in water
[B] 45-60% solution of acetic acid in water
[C] 28-35% solution of acetic acid in water
[D] 5-8% solution of acetic acid in water
Show Answer
Correct Answer: D [5-8% solution of acetic acid in water]
Notes:
5-8% solution of acetic acid in water is called vinegar and is used widely as a preservative in pickles