MCQ practice · SSC Chemistry Board questions · Chapter 6: Concept of Mole and Chemical Counting
How many atoms are present in a molecule of the compound calcium phosphate?
Think it through first, then pick an option.
- a 8
- b 11
- c 13
- d 17
Answer and explanation
Correct answer: c 13
Ca₃(PO₄)₂: 3 Ca, 2 P and 8 O, 3 + 2 + 8 = 13 atoms in all.
Why the other options are wrong
- a 8: 8 counts only the O atoms; adding 3 Ca and 2 P gives 13.
- b 11: 11 is 3 Ca plus 8 O; the 2 P are left out.
- d 17: 17 is the atom count of Fe₂(SO₄)₃ (2 + 3 × 5); Ca₃(PO₄)₂ has 13.
More board questions on this topic
- How many hydrogen atoms are there in 1 mole of water molecules?
- How many atoms are there in one molecule of calcium phosphate?
- The molecular formula H₃PO₄:
- How many atoms are there in one molecule of blue vitriol?
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