Chemistry MCQs
Chemistry Objective (Multiple Choice) General Knowledge Questions & Answers for SSC-CGL, UPPSC, UPSC, NDA, CDS and UPSC Civil Services Prelims Examination.
1. Water at 4 degree centigrade has____?
[A] minimum density
[B] maximum density
[C] No density
[D] None of the above
Show Answer
Correct Answer: B [maximum density]
Notes:
Water at 4 degrees Celsius has maximum density. This is due to the unique molecular structure of water, which allows it to reach its highest density at this temperature. As water cools from higher temperatures, it becomes denser until it reaches 4 degrees. below this temperature, it begins to expand, making ice less dense than liquid water. This phenomenon is crucial for aquatic life, as it allows ice to float, insulating the water below.
2. Which among the following was the first artificially produced element?
[A] Neptunium
[B] Ununbium
[C] Technetium
[D] none of the above
Show Answer
Correct Answer: C [Technetium]
Notes:
Technetium was the first artificially produced element. It was isolated by Carlo Perrier and Emilio Segrè in 1937. Technetium was created by bombarding molybdenum atoms with deuterons that had been accelerated by a device called a cyclotron.
3. F block elements in the periodic table which are commonly called Lanthanides have the following atomic numbers:
[A] 57-70
[B] 57-71
[C] 58-71
[D] 58-70
Show Answer
Correct Answer: B [57-71]
Notes:
The correct answer is 2. The lanthanides are a series of 15 elements in the periodic table, from atomic numbers 57 (Lanthanum) to 71 (Lutetium). They are known for their similar properties and are often found together in nature. The range of atomic numbers for lanthanides is 57 to 71, not 57-70 or 58-70.
4. 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.
5. 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
Show Answer
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.
6. Which of the following metals is extracted and refined in the Mond’s process?
[A] Cobalt
[B] Bismuth
[C] Nickel
[D] Copper
Show Answer
Correct Answer: C [Nickel]
Notes:
The Mond process is a technique to extract and purify nickel. It is also known as the carbonyl process. In this, nickel is heated in a stream of carbon monoxide forming a volatile complex, nickel tetracarbonyl.
7. Which of the following sub-atomic particle accompanies an electron emission in Beta–decay?
[A] antineutrino
[B] neutrino
[C] proton
[D] None of the above
Show Answer
Correct Answer: A [antineutrino]
Notes:
The emission of electron in β−decay is accompanied by the emission of an antineutrino (ν ) and in β+ decay, a neutrino (ν) is generated.
8. Choose the correct statement about d-block elements:
[A] These are the elements of Group 3 to 10
[B] All of them are metals
[C] Both a and b
[D] None
Show Answer
Correct Answer: B [All of them are metals]
Notes:
d-block elements are the elements of Group 3 to 12 in the centre of the Periodic Table. All of them are metals. These are characterised by the filling of inner d orbitals by electrons.
9. What is the PH of human blood?
[A] 8.2
[B] 7.4
[C] 6.5
[D] 7
Show Answer
Correct Answer: B [7.4]
Notes:
Blood is normally slightly basic, with a normal pH range of 7.35 to 7.45. Usually the human body maintains the pH of blood close to 7.40.
10. How many molecules of water Gypsum has, as a water of crystallisation?
[A] 4
[B] 2
[C] 7
[D] 9
Show Answer
Correct Answer: B [2]
Notes:
Gypsum has two molecules of water as water of crystallisation. So, the chemical formula for hydrated gypsum becomes CaSO4.2H2O. This gypsum on getting heated loses water molecules and becomes calcium sulphate hemihydrate (CaSO4.1/2H2O). This is known as plaster of Paris.
