Chemistry MCQs
Chemistry Objective (Multiple Choice) General Knowledge Questions & Answers for SSC-CGL, UPPSC, UPSC, NDA, CDS and UPSC Civil Services Prelims Examination.
1. What characteristic of silica gel, a granular form of silica produced from sodium silicate, enables it to control humidity and prevent spoilage or degradation when packaged with various products?
[A] Its high thermal conductivity
[B] Its hygroscopic properties
[C] Its high reflectivity
[D] Its low thermal conductivity
Show Answer
Correct Answer: B [Its hygroscopic properties]
Notes:
Silica gel possesses hygroscopic properties, meaning it can absorb and hold water vapour. This makes it an effective desiccant or drying agent. When packaged with products, silica gel can help control humidity and prevent spoilage or degradation by absorbing excess moisture. This property is particularly valuable when shipping or storing items that can be negatively impacted by damp conditions, like electronics, food, and leather goods.
2. Which among the following is most advantageous in storage in fuel cells used in small, portable electronics such as phones and laptop computers?
[A] Methanol
[B] Hydrogen
[C] Formic Acid
[D] Acetic Acid
Show Answer
Correct Answer: C [Formic Acid]
Notes:
The cells are called Direct-formic acid fuel cells, in which formic acid is directly fed in the cells. Storage of formic acid is much easier and safer than that of hydrogen because it does not need to be done at high pressures and (or) low temperatures, as formic acid is a liquid at standard temperature and pressure. Formic acid does not cross over the polymer membrane, so its efficiency can be higher than that of methanol. Use of acetic acid in cells does not arise.
3. Who correctly discovered or calculated for subatomic particles?
[A] John Dalton discovered electrons
[B] James Chadwick discovered protons
[C] Rutherford calculated charge to mass ratio of electrons
[D] None of the above
Show Answer
Correct Answer: D [None of the above]
Notes:
J.J. Thomson discovered electrons in 1897. Ernest Rutherford discovered protons in 1917. J.J. Thomson calculated the charge to mass ratio of electrons in 1897. James Chadwick discovered neutrons in 1932. John Dalton proposed the atomic theory in 1808 but did not discover electrons or protons.
4. What is the difference between the mass number of Parent nucleus and Daughter nucleus in an alpha-decay process?
[A] 2
[B] 4
[C] 6
[D] 8
Show Answer
Correct Answer: B [4]
Notes:
In α-decay, the mass number of the product nucleus (daughter nucleus) is four less than that of the decaying nucleus (parent nucleus), while the atomic number decreases by two.
5. What do we call the reaction when an acid and a base react together to form salt and water?
[A] Reduction Reaction
[B] Oxidation Reaction
[C] Neutralisation Reaction
[D] Combination Reaction
Show Answer
Correct Answer: C [Neutralisation Reaction]
Notes:
When an acid and a base react together to form salt and water, the reaction is known as Neutralisation Reaction. HCl (aq) + NaOH (aq) ? H2O (l) + NaCl (aq) (acid) (base) (Water) (Salt) Hydrochloric acid Sodium hydroxide Sodium Chloride
6. From which element in the modern periodic table, the 3d transition series starts?
[A] Zinc
[B] Iron
[C] Scandium
[D] Copper
Show Answer
Correct Answer: C [Scandium]
Notes:
The 3d transition series starts from scandium (Z = 21) and completes at zinc (Z=30). Reason for this transition series is that before the 4p orbital is filled, filling up of 3d orbitals becomes energetically favourable.
7. What is the pH of water in the Acid rain?
[A] More than 12
[B] Less than 5.5
[C] Between 7 and 11
[D] None of the above
Show Answer
Correct Answer: B [Less than 5.5]
Notes:
When pH of rain water is less than 5.5, it is called acid rain. When acid rain flows into the rivers, it lowers the pH of the river water. The survival of aquatic life in such rivers becomes difficult.
8. Which of these alkanes has higher boiling point?
[A] Butane
[B] Methane
[C] Ethane
[D] Hexane
Show Answer
Correct Answer: D [Hexane]
Notes:
There is a steady increase in boiling point with the increase in molecular mass. This is due to the fact that the intermolecular van der Waals forces increase with increase of the molecular size or the surface area of the molecule.
9. Which is the first member of Alkyne series?
[A] Methyne
[B] Acetylene
[C] Propyne
[D] Ethene
Show Answer
Correct Answer: B [Acetylene]
Notes:
The first stable member of alkyne series is ethyne which is popularly known as acetylene. Acetylene is used for arc welding purposes in the form of oxyacetylene flame obtained by mixing acetylene with oxygen gas.
10. Which of the following non-metals is a bright yellow crystalline solid at room temperature?
[A] Selenium
[B] Sulphur
[C] Carbon
[D] Iodine
Show Answer
Correct Answer: B [ Sulphur ]
Notes:
Sulphur is a bright yellow, crystalline solid at room temperature. Sulfur is the fifth most common element on Earth. Its atomic number is 16.
