Question

What is the maximum amount in moles of p2o5 that can theoretically be made from 186 g of p4 and excess oxygen?

Answer 1

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 P4(s) + 10 Cl2(g) → 4 PCl5(g) 


P4 + 5 O2 → 2 P2O5 

(186 g P4) / (123.8950 g/mol) x (2/1) x (141.9447 g/mol) = 426 g P2O5 

Answer 2

Answer : The maximum amount in moles of $P_2O_5$ is, 3 moles

Solution : Given,

Mass of $P_4$ = 186 g

Molar mass of $P_4$ = 123.88 g/mole

First we have to calculate the moles of $P_4$.

$\text{Moles of }P_4=\frac{\text{Mass of }P_4}{\text{Molar mass of }P_4}=\frac{186g}{123.88g/mole}=1.50moles$

Now we have to calculate the moles of $P_2O_5$.

The balanced chemical reaction will be,

$P_4+5O_2\rightarrow 2P_2O_5$

From the balanced reaction, we conclude that

As, 1 mole of $P_4$ react to give 2 moles of $P_2O_5$

So, 1.50 moles of $P_4$ react to give $2\times 1.50=3moles$ of $P_2O_5$

Therefore, the maximum amount in moles of $P_2O_5$ is, 3 moles