Question

How many moles of magnesium phosphate, Mg₃ (PO₄)₂ will contain 0.25mole of oxygen atoms?
(a) 0.02
(b) 3.125 × 10^–2
(c) 1.25 × 10^–2
(d) 2.5 × 10^–2 .

Answer 1

(b) : 1mole of Mg₃ (PO₄ )₂
=> 3moles of Mg atom + 2 moles of P atom + 8 moles of O atom
8 moles of oxygen atoms are present in = 1mole of Mg₃ (PO₄)₂
0.25mole of oxygen atoms are present in = (1 x 0.25)/8

= 3.125 × 10^–2moles of Mg₃ (PO₄ ) ₂.