Question

What volume of oxygen in liters at STP wpuld be required for the combustion of 17.0 grams PH3?

Answer 1

First, we need to state the chemical equation for the combustion of PH3

$4PH3\text{ + 8O2 }\to\text{ P4O10 }+6H2O$

And the mass of PH3 is 17.0 grams and we need to know the moles.

In the periodic table, the atomic mass of the P (phosphorus) is 31 and the atomic mass of the H (hydrogen) is 1.

So, you sum the mass of P to the mass of H multiplied by 3 and you obtain this:

$\text{mole}cu\text{lar weight of PH3=31}\cdot1+1\cdot3=34\text{ g PH3/mol}$

With this data, we can search the moles of PH3: