Question

How many moles of magnesium phosphate $\left(M{g}_3\right(P{O}_4{)}_2)$ will contain $0.25\text{mol}$ of oxygen atoms?

• A. $3.125\times {10}^{-2}\text{mol}$
• B. $1.125\times {10}^{-2}\text{mol}$
• C. $2.5\times {10}^{-2}\text{mol}$
• D. $0.02\text{mol}$

Answer 1

The correct option is A $3.125\times {10}^{-2}\text{mol}$

1 mole of $M{g}_3(P{O}_4{)}_2$ contains 8 moles of 'O' atoms.
8 moles 'O' atoms = 1 mole of $M{g}_3(P{O}_4{)}_2$
0.25 moles of 'O' atoms = $\frac{1}{8}\times 0.25$ moles of $M{g}_3(P{O}_4{)}_2$

$=3.125\times {10}^{-2}\text{mol}$