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 is an example of a Chemical Change?
[A] Rusting of iron
[B] Magnetisation of iron
[C] Melting of iron
[D] Heating of iron
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Correct Answer: A [Rusting of iron ]
Notes:
Rust is an iron oxide, a usually red oxide formed by the redox reaction of iron and oxygen in the presence of water or air moisture. Rusting of Iron is a chemical change.
2. 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.
3. What are the essential components used in the production of Nitrolim, a fertilizer extensively used in the past?
[A] Nitrogen & Limestone
[B] Calcium Carbide and Nitrogen
[C] Calcium Carbide & Carbon
[D] Calcium Carbide and Limestone
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Correct Answer: B [Calcium Carbide and Nitrogen]
Notes:
Nitrolim is a type of fertilizer that was widely used in the past. The main components of Nitrolim are calcium carbide and nitrogen. Calcium carbide reacts with nitrogen to form calcium cyanamide, which is an active ingredient in Nitrolim. This fertilizer is significant as it helps in fixing nitrogen in the soil thereby promoting plant growth.
4. Which gas is produced when an alkali metal, like Lithium or Sodium, reacts with water?
[A] Oxygen
[B] Hydrogen
[C] Ozone
[D] Carbon Dioxide
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Correct Answer: B [Hydrogen]
Notes:
The reaction of alkali metals with water produces Hydrogen gas. These metals are part of the first group on the period table and include lithium, sodium, and potassium. They are known for their vigorous reactions with water, which results in the liberation of hydrogen gas. Along with the gas, this reaction also forms a basic alkali metal hydroxide, which gives the solution its characteristic basic or alkaline properties.
5. Hard Water contains which of the following ?
[A] Aluminum
[B] Chlorine
[C] Calcium
[D] Zinc
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Correct Answer: C [Calcium]
Notes:
Hard water is generally found in areas where groundwater is in contact with limestone, chalk and dolomite and gets higher amount of calcium and magnesium dissolved in it.
6. Kazimierz Funk or Casimir Funk, was a Polish biochemist, generally credited with the first formulation of the concept of which of the following ?
[A] Amino Acids
[B] DNA
[C] RNA
[D] Vitamins
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Correct Answer: D [Vitamins]
Notes:
Kazimierz Funk (1884 – 1967) was a Polish biochemist, and one of the first to formulate the concept of Vitamins.
7. Steel is an alloy consisting mostly of iron, with a carbon content between 0.2% and 2.1% by weight. An increasing amount of Iron will result in which of the following?
[A] Increase Hardening
[B] Decrease Hardening
[C] Increase ductility
[D] Increase melting Point
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Correct Answer: A [Increase Hardening]
Notes:
Increasing the amount of iron in steel generally leads to increased hardening. This is due to the formation of a solid solution where carbon atoms occupy interstitial spaces in the iron lattice, enhancing strength and hardness. Steel’s carbon content is crucial. higher carbon levels (up to 2.1%) improve hardness but reduce ductility. The melting point of steel is also influenced by its composition, but the primary effect of increasing iron is hardening.
8. Carbon monoxide poisoning is the most common type of fatal air poisoning in many parts of the world. What makes it such a fatal gas?
[A] CO dissolves in cytoplasm and functions as an inhibitor of the crucial enzymes for metabolism
[B] CO competes with Haemoglobin for Oxygen intake
[C] CO dissolves in blood Plasma and spreads toxicity
[D] CO converts into Carbon Dioxide in presence of water in Blood
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Correct Answer: B [ CO competes with Haemoglobin for Oxygen intake]
Notes:
Carbon monoxide is colourless, odourless, and tasteless, but highly toxic because it combines with haemoglobin to produce carboxyhemoglobin, which usurps the space in haemoglobin that normally carries oxygen, but is ineffective for delivering oxygen to bodily tissues. Concentrations as low as 667 ppm may cause up to 50% of the body’s hemoglobin to convert to carboxyhemoglobin. The impact is irreversible and that is why that even after available of oxygen, the carboxyhemoglobin does not allow the Oxygen to be taken up.
9. Which of the following chemicals is resposible for temporary acid rain in colder regions?
[A] Hydrogen chloride
[B] Sulphur dioxide
[C] Nitric acid
[D] Nitrogen oxides
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Correct Answer: A [ Hydrogen chloride]
Notes:
Hydrogen chloride gas released from volcanic eruption is responsible for temporary acid rain in colder regions.
10. 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.