Question

A sample of ammonium phosphate, contains 18 moles of hydrogen atoms . The number of moles of oxygen atoms in this sample is

Answer 1

1mole of (NH4) 3PO4) contains 12 moles of H atoms
So no. Of moles of (NH4) 3PO4) is 1.5
No.of moles of O atoms =1.5×4=6 atoms

Answer 2

The number of moles of oxygen atoms is 6

Given:

No. of moles of hydrogen atoms in ammonium phosphate sample = 18 moles.

Solution:

The formula for Ammonium phosphate is = $(NH_4)_3PO_4$

We can observe from the formula, that the number of hydrogen atoms = 12

Likewise, No. of N atoms = 3

No. of P atoms = 1

No. of O atoms = 4

This implies that 12 moles of Hydrogen correspond to 3 moles of oxygen.

Let x moles of oxygen correspond to 18 moles of hydrogen.

Therefore,  

$\frac{x}{4}=\frac{18}{12}$

$\Rightarrow$ x = 6