MCQ practice · SSC Chemistry Board questions · Chapter 6: Concept of Mole and Chemical Counting
How many atoms are there in one molecule of blue vitriol?
Think it through first, then pick an option.
- a 5
- b 6
- c 11
- d 21
Answer and explanation
Correct answer: d 21
CuSO₄·5H₂O: 1 Cu, 1 S, 9 O and 10 H, 21 atoms in all.
Why the other options are wrong
- a 5: 5 is just the number of water molecules; blue vitriol has 21 atoms in all.
- b 6: 6 counts only the CuSO₄ part; adding the 15 atoms of 5H₂O gives 21.
- c 11: 11 does not count all of the water part; Cu 1 + S 1 + O 9 + H 10 = 21.
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