A sample of ammonium phosphate, `(NH_4)_3PO_4` contains` 18` moles of hydrogen atoms. The number of moles of oxygen atoms in the sample is

Options

A. `6`
B. `18`
C. `4`
D. `24`

Answer

To solve the problem, we need to determine the number of moles of oxygen atoms in a sample of ammonium phosphate, given that it contains 18 moles of hydrogen atoms.

### Step-by-Step Solution:

1. **Identify the Chemical Formula**: The chemical formula for ammonium phosphate is \((NH_4)_3PO_4\).

2. **Determine the Number of Hydrogen Atoms per Mole**: From the formula, we can see that each ammonium ion \((NH_4^+)\) contains 4 hydrogen atoms. Since there are 3 ammonium ions in the formula, the total number of hydrogen atoms in one mole of ammonium phosphate is:
\[ 3 \times 4 = 12 \text{ hydrogen atoms} \]

3. **Calculate the Moles of Ammonium Phosphate**: We know that the sample contains 18 moles of hydrogen atoms. To find out how many moles of ammonium phosphate this corresponds to, we can set up a ratio:
\[ \text{Moles of } (NH_4)_3PO_4 = \frac{\text{Moles of H}}{12} \]
Substituting the values:
\[ \text{Moles of } (NH_4)_3PO_4 = \frac{18}{12} = 1.5 \text{ moles} \]

4. **Determine the Number of Oxygen Atoms per Mole of Ammonium Phosphate**: From the formula \((NH_4)_3PO_4\), we can see that there is 1 phosphate group \((PO_4^{3-})\) which contains 4 oxygen atoms. Therefore, each mole of ammonium phosphate contains 4 moles of oxygen atoms.

5. **Calculate the Total Moles of Oxygen Atoms**: Now, we can find the total number of moles of oxygen atoms in the sample:
\[ \text{Moles of O} = \text{Moles of } (NH_4)_3PO_4 \times 4 \]
Substituting the value we found:
\[ \text{Moles of O} = 1.5 \times 4 = 6 \text{ moles} \]

### Final Answer:
The number of moles of oxygen atoms in the sample is **6 moles**.

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