The total number of neutrons present in `54mL H_2O(l)` are :

Options

A. `3 N_(A)`
B. `30 N_(A)`
C. ` 24 N_(A)`
D. None of these

Answer

To find the total number of neutrons present in 54 mL of water (H₂O), we can follow these steps:

### Step 1: Calculate the mass of water
Given that the density of water is 1 g/mL, we can calculate the mass of 54 mL of water.

\[ \text{Mass} = \text{Density} \times \text{Volume} = 1 \, \text{g/mL} \times 54 \, \text{mL} = 54 \, \text{g} \]

### Step 2: Calculate the number of moles of water
To find the number of moles of water, we use the formula:

\[ \text{Number of moles} = \frac{\text{Mass}}{\text{Molar mass}} \]

The molar mass of water (H₂O) is calculated as follows:

\[ \text{Molar mass of H₂O} = (2 \times 1) + 16 = 18 \, \text{g/mol} \]

Now we can calculate the number of moles:

\[ \text{Number of moles of H₂O} = \frac{54 \, \text{g}}{18 \, \text{g/mol}} = 3 \, \text{moles} \]

### Step 3: Determine the composition of water
Each molecule of water (H₂O) consists of:
- 2 Hydrogen (H) atoms
- 1 Oxygen (O) atom

### Step 4: Calculate the number of neutrons in one molecule of water
- **Hydrogen (H)**: The mass number (A) of hydrogen is 1, and the atomic number (Z) is 1. Therefore, the number of neutrons in hydrogen is:

\[ \text{Number of neutrons in H} = A - Z = 1 - 1 = 0 \]

- **Oxygen (O)**: The mass number (A) of oxygen is 16, and the atomic number (Z) is 8. Therefore, the number of neutrons in oxygen is:

\[ \text{Number of neutrons in O} = A - Z = 16 - 8 = 8 \]

### Step 5: Calculate the total number of neutrons in 3 moles of water
In one molecule of water, there are 8 neutrons from the oxygen atom and 0 from the hydrogen atoms. Therefore, in one molecule of water, there are 8 neutrons.

Now, we need to find the total number of molecules in 3 moles of water:

\[ \text{Total number of molecules} = 3 \, \text{moles} \times 6.022 \times 10^{23} \, \text{molecules/mole} = 1.8066 \times 10^{24} \, \text{molecules} \]

Now, we can calculate the total number of neutrons:

\[ \text{Total number of neutrons} = \text{Number of neutrons per molecule} \times \text{Total number of molecules} \]
\[ \text{Total number of neutrons} = 8 \times 1.8066 \times 10^{24} = 1.44528 \times 10^{25} \]

### Final Answer
The total number of neutrons present in 54 mL of water is approximately \( 1.44528 \times 10^{25} \).

---