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 colour does cobalt oxide impart to glass?
[A] Brown
[B] Blue
[C] Red
[D] Yellow
Show Answer
Correct Answer: B [Blue]
Notes:
Cobalt Oxide is commonly used to create a distinctive blue hue in glasses and ceramics. The depth of the blue can be altered by changing the concentration of the oxide. In addition to being used for aesthetic purposes, Cobalt blue, which results from Cobalt Oxide, is also used because it absorbs certain wavelengths of light, making it useful for filtering out unwanted wavelengths.
3. An Jewellery was left exposed to the atmosphere for some time and it becomes coated with green carbonate. The Jewellery is made up of which of the following?
[A] Copper
[B] Silver
[C] Zinc
[D] Gold
Show Answer
Correct Answer: A [Copper]
Notes:
The correct answer is Copper. When copper jewelry is exposed to air and moisture, it reacts with carbon dioxide and water, forming copper carbonate, which appears as a green patina (often called verdigris). This process is known as oxidation. Unlike copper, silver and gold do not typically form green coatings. silver may tarnish to a black color due to silver sulfide formation, while gold is highly resistant to corrosion and tarnishing.
4. Argon is the third most common gas in the Earth’s atmosphere, at 0.93%. This gas is generated due to decay of which among the following isotopes in the Earth’s crust ?
[A] K-40
[B] Ca-40
[C] Ca-48
[D] K-41
Show Answer
Correct Answer: A [K-40]
Notes:
Potassium-40 is a radioactive isotope of potassium with a long half-life of 1.251×10⁹ years. The decay of this particular isotope explains the large abundance of argon (0.93%) in the Earth’s atmosphere.
5. Aluminum is getting popular worldwide today as a “Green Metal”. Which among the following properties of Aluminum makes it a Green Metal?
[A] Aluminum has been providing a replacement of wood for saving forests and contributes in environment protection
[B] Aluminum is a light metal and it is resistant to corrosion
[C] Aluminum has fairly high rate of recycling and it can be re-used repeatedly without its quality deteriorating
[D] The lands after the Bauxite mining can be restored very quickly and easily
Show Answer
Correct Answer: C [Aluminum has fairly high rate of recycling and it can be re-used repeatedly without its quality deteriorating]
Notes:
Aluminum is considered a “Green Metal” primarily due to its high recycling rate. Approximately 75% of all aluminum ever produced is still in use today, as it can be recycled indefinitely without losing quality. This process saves energy—recycling aluminum uses about 95% less energy than producing new aluminum from bauxite ore. Additionally, recycling reduces greenhouse gas emissions and conserves natural resources, making aluminum a sustainable choice in various applications.
6. 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.
7. Which of these is NOT a compound of carbon?
[A] Acetic acid
[B] Chloroform
[C] Caustic Soda
[D] Methane
Show Answer
Correct Answer: C [Caustic Soda]
Notes:
Caustic soda is a compound of sodium where as Acetic acid, Chloroform and Methane are the compounds of carbon.
8. Which of the following quantum numbers is not necessary to identify an orbital?
[A] Principal quantum number
[B] Azimuthal quantum number
[C] Magnetic quantum number
[D] Electron Spin quantum number
Show Answer
Correct Answer: D [Electron Spin quantum number]
Notes:
An orbital is identified by the set of 3 quantum numbers: Principal quantum number, Azimuthal quantum number and magnetic quantum number.
9. Which of the following gas is used to prevent the chips from getting oxidised?
[A] Oxygen
[B] Nitrogen
[C] Helium
[D] Lithium
Show Answer
Correct Answer: B [Nitrogen]
Notes:
The chips manufacturers usually flush bags of chips with gas such as nitrogen to prevent the chips from getting oxidised.
10. What is the sum of powers of the concentration of the reactants called as?
[A] Order of reaction
[B] Stage of reaction
[C] Zone of reaction
[D] None of the above
Show Answer
Correct Answer: A [Order of reaction]
Notes:
The sum of powers of the concentration of the reactants in the rate law expression is known as the order of that chemical reaction.
