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 of the following are the most and the least electronegative elements in the periodic table?
[A] Fluorine and Caesium
[B] Hydrogen and Helium
[C] Carbon and Oxygen
[D] Chlorine and Fluorine
Show Answer
Correct Answer: A [Fluorine and Caesium]
Notes:
Caesium is the least electronegative element in the periodic table and Fluorine is the most electronegative. Electronegativity is a measure of the tendency of an atom to attract a bonding pair of electrons.
2. Which among the following metal is highest electrical conductivity as well as highest thermal conductivity?
[A] Gold
[B] Silver
[C] Platinum
[D] Iron
Show Answer
Correct Answer: B [Silver]
Notes:
Silver is the metal with the highest electrical and thermal conductivity. It has only one valence electron, which can move around with little resistance. This makes silver a great conductor of electricity and heat.
Silver’s thermal conductivity is 430 wK/m, which is higher than copper (400 wK/m), aluminum (235 wK/m), and brass (109 wK/m).
Silver’s low contact wear resistance and excellent optical reflectivity make it ideal for coating contacts, mirrors, and conductors in telecom applications.
Impurities can decrease a conductor’s conductivity. For example, sterling silver is not as good of a conductor as pure silver. Oxidized silver is not as good a conductor as untarnished silver.
3. 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.
4. Duralumin which is used in making aero planes is an alloy consisting of _____?
[A] Aluminum & Copper
[B] Aluminum, Copper & Manganese
[C] Aluminum, Copper, Manganese & Magnesium
[D] Aluminum and zinc
Show Answer
Correct Answer: C [Aluminum, Copper, Manganese & Magnesium]
Notes:
Duralumin is an alloy primarily composed of aluminum, copper, manganese, and magnesium. It was developed in the early 20th century and is known for its high strength-to-weight ratio, making it ideal for aircraft construction. The addition of copper enhances strength, while manganese and magnesium improve corrosion resistance and workability. Duralumin was first used in aircraft during World War I, revolutionizing aviation materials.
5. Normal” rainfall is slightly acidic (and a pH of 5.6 has been assigned which might be somewhere near 5 ) because of the presence of _______?
[A] Nitric Oxide
[B] Sulphuric Acid
[C] Nitric Acid
[D] Carbonic Acid
Show Answer
Correct Answer: D [Carbonic Acid]
Notes:
Normal rainfall is slightly acidic due to the presence of carbonic acid, which forms when carbon dioxide (CO2) dissolves in water. The pH of normal rainwater is typically around 5.6, making it mildly acidic. This natural acidity is a result of the CO2 in the atmosphere, which is produced by respiration, combustion, and other natural processes.
6. When a piece of quicklime is dipped in water, it gives bubbles. This bubbling is due to which of the following ?
[A] Oxygen
[B] Carbon Dioxide
[C] Water Vapour
[D] Hydrogen
Show Answer
Correct Answer: C [Water Vapour]
Notes:
When quicklime (calcium oxide) is added to water, it reacts exothermically to form calcium hydroxide (slaked lime). This reaction produces heat and releases water vapor, which causes bubbling. The reaction can be represented as: [ ext{CaO} + ext{H}_2 ext{O}
ightarrow ext{Ca(OH)}_2 + ext{heat} ] Trivia: Quicklime is used in various applications, including steelmaking and water treatment, and was historically used in ancient construction.
7. Which among the following will emit maximum mass of carbon dioxide , when the same quantity is burnt of all of them?
[A] Kerosene
[B] Natural Gas
[C] Gasoline
[D] Propane
Show Answer
Correct Answer: A [Kerosene]
Notes:
The carbon content of Kerosene is higher than the other fuels mentioned in the option, that is why it will emit maximum mass of carbon dioxide, when the same quantity is burnt.
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
Show Answer
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. What is the atomic number of Barium?
[A] 54
[B] 56
[C] 58
[D] 60
Show Answer
Correct Answer: B [56]
Notes:
The atomic number of barium is 56.
10. Which of the following compound of sodium is generally prepared by Solvay process?
[A] Sodium Carbonate
[B] Sodium Hydroxide
[C] Sodium Chloride
[D] All of the above
Show Answer
Correct Answer: A [Sodium Carbonate]
Notes:
Sodium carbonate is generally prepared by Solvay Process.