<u>Answer:</u> The amount of
formed is 469.8 grams.
<u>Explanation:</u>
To calculate the number of moles, we use the equation:
......(1)
Given mass of phosphine = 225 g
Molar mass of phosphine = 34 g/mol
Putting values in equation 1, we get:

The given chemical reaction follows:

Assuming that oxygen gas is present in excess, it is considered as an excess reagent.
Phosphine is considered as a limiting reagent because it limits the formation of product.
By Stoichiometry of the reaction:
4 moles of phosphine produces 1 mole of 
So, 6.62 moles of phosphine will produce =
of 
Now, calculating the mass of
by using equation 1:
Molar mass of
= 283.9 g/mol
Moles of
= 1.655 moles
Putting values in equation 1, we get:

Hence, the amount of
formed is 469.8 grams.