MCQ practice · SSC Chemistry Board questions · Chapter 6: Concept of Mole and Chemical Counting
How many atoms are there in magnesium phosphate?
Think it through first, then pick an option.
- a 6
- b 8
- c 11
- d 13
Answer and explanation
Correct answer: d 13
Mg₃(PO₄)₂ has 3 + 2 + 2 × 4 = 13 atoms.
Why the other options are wrong
- a 6: 6 comes from the wrong formula MgPO₄; the right one, Mg₃(PO₄)₂, has 13.
- b 8: 8 counts only the O atoms (2 × 4 in 2 PO₄); Mg and P are left out.
- c 11: 11 is 3 Mg and 8 O; the 2 P are left out.
More board questions on this topic
- How many atoms are there in one molecule of potassium dichromate?
- How many atoms are there in one molecule of aluminium nitrate?
- What is the relative atomic mass of an element whose one atom has…
- How many moles are there in 100 g of potassium dichromate?
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