Basic Concepts of Chemistry – Multiple Choice Questions (MCQs)

1. 49. Which of the following is a pure substance?

   • A. Air
   • B. Milk
   • C. Gold
   • D. Sea water

2. 50. The smallest particle of an element that retains the chemical identity of the element is a/an:

   • A. Atom
   • B. Molecule
   • C. Ion
   • D. Compound

3. 51. The velocity of light in a vacuum is approximately:

   • A. 3 x 10^8 m/s
   • B. 3 x 10^7 m/s
   • C. 3 x 10^9 m/s
   • D. 3 x 10^6 m/s