Chirkut.বাংলা

MCQ practice · SSC Chemistry Board questions · Chapter 9: Acid-Base Balance

Dhaka Board 2024

How many molecules of water are attached in washing soda?

Think it through first, then pick an option.

  1. a 24
  2. b 10
  3. c 7
  4. d 5
Answer and explanation

Correct answer: b 10

Washing soda is Na₂CO₃·10H₂O, so 10 water molecules.

Why the other options are wrong

  • a 24: Not 24; the formula Na₂CO₃·10H₂O shows 10 water molecules.
  • c 7: Not 7; it carries 10 molecules of water.
  • d 5: Not 5; it carries 10 molecules of water.