Question

what is the maximum amount of moles of P2O5 that can theoretically be made from 136 g of P4 and excess oxygen

Answer 1

We are given with
136 g P4
excess oxygen

The complete combustion reaction is
P4 + 5O2 => 2P2O5
Converting the amount of P4 to moles
136/123.9 = 1.098 moles

Using stoichiometry
moles P2O5 = 1.098 x 2 = 2.195 moles P2O5

Answer 2

Answer: The maximum number of moles of $P_2O_5$ theoretically made is 2.194 moles.

Explanation:

To calculate the number of moles, we use the equation

$\text{Number of moles}=\frac{\text{Given mass}}{\text{Molar mass}}$

Given mass of $P_4$ = 136 g

Molar mass of $P_4$ = 123.9 g/mol

Putting values in above equation, we get:

$\text{Moles of }P_4=\frac{136g}{123.9g/mol}=1.097mol$

The chemical equation for the formation of $P_2O_5$ follows:

$P_4+5O_2\rightarrow 2P_2O_5$

Oxygen is present in excess, so it is considered as an excess reagent.

$P_4$ is considered as a limiting reagent because it limits the formation of product.

By Stoichiometry of the reaction:

If 1 mole of $P_4$ is producing 2 moles of $P_2O_5$

So, 1.097 moles of $P_4$ will produce = $\frac{2}[1}\times 1.097=2.194mol$ of $P_2O_5$

Hence, the maximum number of moles of $P_2O_5$ theoretically made is 2.194 moles.