Question

If 2.0 moles of P4 are used, how many moles of P2O3 are formed?

Answer 1

1) Write the chemical equation.

$P_4+O_2\rightarrow P_2O_3$

2) List the know and unknown quantities.

Reactants

P: 4

O: 2

Products

P: 2

O: 3

3) Balance P.

$P_4+O_2\operatorname{\rightarrow}2P_2O_3$

Reactants

P: 4

O: 2

Products

P: 4

O: 6

4) Balance O.

$P_4+3O_2\operatorname{\rightarrow}2P_2O_3$

5) Moles of P2O3.

The molar ratio between P4 and P2O3 is 1 mol P4: 2 mol P2O3.

$mol\text{ }P_2O_3=2.0\text{ }mol\text{ }P_4*\frac{2\text{ }mol\text{ }P_2O_3}{1\text{ }mol\text{ }P_4}=4.0\text{ }mol\text{ }P_2O_3$

If 20 mol P4 are used, 4.0 mol P2O3 are formed.

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