What is the number of moles of O-atoms in 126 amu of `HNO_3` ?

Options

A. 2
B. `(2)/(N_(A))`
C. `0.1 N_(A)`
D. ` (6)/(N_(A))`

Answer

To solve the problem of finding the number of moles of oxygen atoms in 126 amu of HNO₃, we can follow these steps:

### Step 1: Calculate the molar mass of HNO₃
The molar mass of HNO₃ can be calculated by adding the atomic masses of its constituent elements:
- Hydrogen (H) = 1 amu
- Nitrogen (N) = 14 amu
- Oxygen (O) = 16 amu (and there are 3 oxygen atoms)

So, the molar mass of HNO₃ is:
\[ \text{Molar mass of HNO}_3 = 1 + 14 + (16 \times 3) = 1 + 14 + 48 = 63 \text{ g/mol} \]

### Step 2: Convert 126 amu to grams
Since 1 amu is equivalent to 1 g/mol, we can directly use the given mass in amu as grams for our calculations. Therefore, 126 amu is equivalent to 126 grams.

### Step 3: Calculate the number of moles of HNO₃
Using the formula for calculating moles:
\[ \text{Number of moles} = \frac{\text{mass (g)}}{\text{molar mass (g/mol)}} \]
Substituting the values we have:
\[ \text{Number of moles of HNO}_3 = \frac{126 \text{ g}}{63 \text{ g/mol}} = 2 \text{ moles} \]

### Step 4: Calculate the number of moles of oxygen atoms
From the chemical formula HNO₃, we see that each molecule of HNO₃ contains 3 oxygen atoms. Therefore, the number of moles of oxygen atoms can be calculated as follows:
\[ \text{Number of moles of O atoms} = \text{Number of moles of HNO}_3 \times 3 \]
Substituting the number of moles of HNO₃:
\[ \text{Number of moles of O atoms} = 2 \text{ moles} \times 3 = 6 \text{ moles} \]

### Final Answer
The number of moles of oxygen atoms in 126 amu of HNO₃ is **6 moles**.

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