Chemistry MCQs
Chemistry Objective (Multiple Choice) General Knowledge Questions & Answers for SSC-CGL, UPPSC, UPSC, NDA, CDS and UPSC Civil Services Prelims Examination.
1. The atomic weight of Chlorine is 35. It consists of _______?
[A] 17 Protons + 18 Neutrons
[B] 17 Neutrons + 18 protons
[C] 17 Neutrons + 17 Protons + 1 electron
[D] None of the above
Show Answer
Correct Answer: A [17 Protons + 18 Neutrons]
Notes:
Chlorine has an atomic number of 17, meaning it has 17 protons. Its atomic weight is approximately 35, which indicates it typically has 18 neutrons (35 – 17 = 18). Therefore, the correct composition is 17 protons and 18 neutrons. Chlorine is a halogen and exists primarily as two stable isotopes: Chlorine-35 and Chlorine-37.
2. PAN (Peroxyacetyl nitrate) is a secondary gaseous compound found in _?
[A] Classical smog
[B] Volatile organic compound
[C] Photochemical smog
[D] Green manure
Show Answer
Correct Answer: C [ Photochemical smog]
Notes:
Third option is the correct answer
Photochemical smog is the chemical reaction of sunlight, nitrogen oxides and volatile organic compounds in the atmosphere, which leaves airborne particles and ground-level ozone.
3. Which of the following chemicals is also known as “Chinese snow”?
[A] Silver iodide
[B] Potassium nitrate
[C] Ammonium chloride
[D] Sodium phosphate
Show Answer
Correct Answer: B [ Potassium nitrate]
Notes:
Potassium nitrate is one of several nitrogen-containing compounds collectively referred to as saltpetre or saltpetre. It is also known as “Chinese snow”. Major uses of potassium nitrate are in fertilizers, rocket propellants and fireworks.
4. 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.
5. What can be the maximum number of electrons in a shell, if principal quantum number is n?
[A] n
[B] n2
[C] 2n2
[D] 3n3
Show Answer
Correct Answer: C [2n2]
Notes:
The general formula is that the nth shell can hold up to 2n2 electrons. For example: for L shell n =2, so maximum number of electrons will be 2(22) i.e. 8.
6. What is Zeeman effect?
[A] splitting of spectral line in presence of magnetic field
[B] splitting of spectral line in presence of electric field
[C] convergence of spectral line in presence of magnetic field
[D] convergence of spectral line in presence of electric field
Show Answer
Correct Answer: A [splitting of spectral line in presence of magnetic field]
Notes:
Zeeman effect refers to the splitting of a spectrum line into several components by the application of a magnetic field. It is named after the Dutch physicist Pieter Zeeman.
7. What do we call the difference between the initial mass energy and the total mass energy of the decay products in a radioactive decay?
[A] entropy
[B] disintegration energy
[C] alpha energy
[D] integration energy
Show Answer
Correct Answer: B [disintegration energy]
Notes:
The disintegration energy or the Q-value of a nuclear reaction is the difference between the initial mass energy and the total mass energy of the decay products.
8. What is the multiplication factor when the nuclear reactor is said to be critical?
[A] 0
[B] 1
[C] 2
[D] 10
Show Answer
Correct Answer: B [1]
Notes:
The multiplication factor is the measure of the growth rate of the neutrons in the reactor. For K = 1, the operation of the reactor is said to be critical.
9. What do we call the ratio of number of fission produced by a given generation of neutrons to the number of fission of the preceding generation?
[A] Critical factor
[B] Energy factor
[C] Multiplication factor
[D] Moderation factor
Show Answer
Correct Answer: C [Multiplication factor]
Notes:
The multiplication factor is the ratio of number of fission produced by a given generation of neutrons to the number of fission of the preceding generation.
10. Which of the following is a part of chalcogen group of the modern periodic table?
[A] Boron
[B] Tin
[C] Lead
[D] Oxygen
Show Answer
Correct Answer: D [Oxygen]
Notes:
The chalcogens are the group 16 elements of the periodic table. This group is also known as the oxygen family. It consists of the elements oxygen (O), sulphur (S), selenium (Se), tellurium (Te), and the radioactive element polonium (Po).
