Question

How many moles of P4 are needed to react with 9 moles of Mg? 6 Mg + P4 → 2 Mg3P2

Answer 1

Let us look at the equation;

6Mg + P4 .............>2 Mg3 P2

according to this equation 1 mole of P4 reacts with 6 moles of Mg. So my recipe is 1 mole of P4is required for every 6 moles of Mg.

1 mole of P4 / 6 moles of Mg ......(a)

X moles of P4 completely reacts with 9 moles of Mg

X moles of P4 / 9 moles of Mg ......(b)

the two ratios are equal.

(a) = (b)

1 mole of P4 / 6 moles of Mg =

X moles of P4 / 9 moles of Mg

1 = X .6

6X = 9

X = 9/6 = 3/2 = 1.5 mole