Free Class 12 Chemistry MCQs – NCERT-Based Practice
Free Class 12 Chemistry MCQs – Online Practice — Practice Questions
1. Which of the following is an intensive property?
- (A) Mass
- (B) Volume
- (C) Density
- (D) Number of moles
Answer: (C) Density
Density is an intensive property because it does not depend on the amount of substance.
2. According to Raoult's law, the vapour pressure of an ideal solution is directly proportional to the:
- (A) Molar mass of the solute
- (B) Mole fraction of the solvent
- (C) Density of the solution
- (D) Temperature only
Answer: (B) Mole fraction of the solvent
Raoult's law states that the partial vapour pressure of the solvent is proportional to its mole fraction.
3. Which of the following is a colligative property?
- (A) Surface tension
- (B) Osmotic pressure
- (C) Viscosity
- (D) Density
Answer: (B) Osmotic pressure
Osmotic pressure depends only on the number of solute particles and is a colligative property.
4. The oxidation number of chromium in K₂Cr₂O₇ is:
- (A) +3
- (B) +4
- (C) +6
- (D) +7
Answer: (C) +6
The oxidation state of chromium in potassium dichromate is +6.
5. Which electrode is used as the standard reference electrode?
- (A) Copper electrode
- (B) Zinc electrode
- (C) Standard hydrogen electrode
- (D) Silver electrode
Answer: (C) Standard hydrogen electrode
The Standard Hydrogen Electrode (SHE) has a standard electrode potential of 0.00 V.
6. The unit of molar conductivity is:
- (A) S cm² mol⁻¹
- (B) S cm⁻¹
- (C) Ω cm
- (D) Ω⁻¹
Answer: (A) S cm² mol⁻¹
Molar conductivity is expressed as S cm² mol⁻¹.
7. The half-life of a first-order reaction is:
- (A) Directly proportional to concentration
- (B) Inversely proportional to concentration
- (C) Independent of initial concentration
- (D) Zero
Answer: (C) Independent of initial concentration
The half-life of a first-order reaction remains constant irrespective of the initial concentration.
8. Which catalyst is used in the Haber process?
- (A) Nickel
- (B) Iron
- (C) Platinum
- (D) Vanadium pentoxide
Answer: (B) Iron
Finely divided iron acts as the catalyst in the Haber process for ammonia synthesis.
9. Which of the following is a lanthanoid element?
- (A) Scandium
- (B) Cerium
- (C) Titanium
- (D) Zinc
Answer: (B) Cerium
Cerium (Ce) belongs to the lanthanoid series.
10. The IUPAC name of [Cu(NH₃)₄]SO₄ is:
- (A) Copper tetraammine sulfate
- (B) Tetraamminecopper(II) sulfate
- (C) Copper(II) ammonia sulfate
- (D) Ammine copper sulfate
Answer: (B) Tetraamminecopper(II) sulfate
The correct IUPAC name is Tetraamminecopper(II) sulfate.
11. Which alkyl halide undergoes SN1 reaction most readily?
- (A) CH₃Cl
- (B) C₂H₅Cl
- (C) (CH₃)₃CCl
- (D) CH₃CH₂CH₂Cl
Answer: (C) (CH₃)₃CCl
Tertiary alkyl halides form the most stable carbocations and therefore undergo SN1 reactions most readily.
12. Phenol is more acidic than ethanol because:
- (A) Phenol has higher molecular mass
- (B) Phenoxide ion is resonance stabilized
- (C) Ethanol has hydrogen bonding
- (D) Ethanol contains more hydrogen atoms
Answer: (B) Phenoxide ion is resonance stabilized
The phenoxide ion is stabilized by resonance, increasing the acidity of phenol.
13. Which reagent converts ethanol into ethanal?
- (A) LiAlH₄
- (B) PCC
- (C) NaBH₄
- (D) H₂/Ni
Answer: (B) PCC
PCC (Pyridinium chlorochromate) oxidizes primary alcohols to aldehydes.
14. Which functional group is present in glucose?
- (A) Ketone only
- (B) Aldehyde and hydroxyl
- (C) Carboxylic acid
- (D) Ester
Answer: (B) Aldehyde and hydroxyl
Glucose is an aldohexose containing one aldehyde group and multiple hydroxyl groups.
15. Which vitamin is known as ascorbic acid?
- (A) Vitamin A
- (B) Vitamin C
- (C) Vitamin D
- (D) Vitamin K
Answer: (B) Vitamin C
Vitamin C is chemically known as ascorbic acid.
16. Nylon-6,6 is prepared by the condensation of:
- (A) Ethylene glycol and terephthalic acid
- (B) Hexamethylenediamine and adipic acid
- (C) Styrene molecules
- (D) Caprolactam only
Answer: (B) Hexamethylenediamine and adipic acid
Nylon-6,6 is formed by condensation polymerization of hexamethylenediamine and adipic acid.
17. Which drug is commonly used as an antacid?
- (A) Aspirin
- (B) Omeprazole
- (C) Magnesium hydroxide
- (D) Paracetamol
Answer: (C) Magnesium hydroxide
Magnesium hydroxide neutralizes excess stomach acid and acts as an antacid.
18. Which of the following biomolecules acts as the primary source of energy in living organisms?
- (A) Proteins
- (B) Carbohydrates
- (C) Vitamins
- (D) Nucleic acids
Answer: (B) Carbohydrates
Carbohydrates are the primary source of energy for cells.
19. Which of the following obeys the octet rule completely?
- (A) BF₃
- (B) PCl₅
- (C) NH₃
- (D) SF₆
Answer: (C) NH₃
Nitrogen in NH₃ has eight electrons in its valence shell, satisfying the octet rule.
20. Which gas is evolved when sodium bicarbonate reacts with dilute hydrochloric acid?
- (A) Hydrogen
- (B) Oxygen
- (C) Carbon dioxide
- (D) Chlorine
Answer: (C) Carbon dioxide
Sodium bicarbonate reacts with hydrochloric acid to produce sodium chloride, water and carbon dioxide gas.