Basic Concepts of Chemistry – Multiple Choice Questions (MCQs)

1. 37. Which of the following is a heterogeneous mixture?

   • A. Sugar solution
   • B. Salt solution
   • C. Smoke
   • D. Brass

2. 38. The chemical formula of chalk is:

   • A. CaCO3
   • B. CaO
   • C. Ca(OH)2
   • D. CaSO4

3. 39. How many moles of water are present in 36 g of water?

   • A. 2 moles
   • B. 1 mole
   • C. 3 moles
   • D. 0.5 moles

4. 40. The term 'molecular mass' is used for:

   • A. Molecules
   • B. Atoms
   • C. Ions
   • D. Elements

5. 41. The empirical formula of hydrogen peroxide is:

   • A. HO
   • B. H2O2
   • C. H2O
   • D. OH

6. 42. The value of Avogadro's number is equal to the number of atoms in:

   • A. 12 g of C-12
   • B. 1 g of H-1
   • C. 16 g of O-16
   • D. 32 g of S-32

7. 43. Which of the following has the highest number of atoms?

   • A. 1 g O2
   • B. 1 g H2
   • C. 1 g N2
   • D. 1 g CH4

8. 44. The number of moles of NaCl in 58.5 g of NaCl is:

   • A. 1 mol
   • B. 0.5 mol
   • C. 2 mol
   • D. 0.1 mol

9. 45. The correct scientific notation for 0.0000078 is:

   • A. 7.8 x 10^-6
   • B. 7.8 x 10^6
   • C. 78 x 10^-7
   • D. 0.78 x 10^-5

10. 46. What is the equivalent weight of an element?

    • A. Atomic weight / valency
    • B. Atomic weight x valency
    • C. Atomic weight + valency
    • D. Atomic weight - valency

11. 47. A reaction in which heat is absorbed from the surroundings is called:

    • A. Endothermic reaction
    • B. Exothermic reaction
    • C. Neutralization reaction
    • D. Redox reaction

12. 48. The mass of one molecule of SO2 is:

    • A. 64 amu
    • B. 32 amu
    • C. 48 amu
    • D. 16 amu