Calculate the number of moles :
5.0 L of 0.75 M `Na_(2)CO_(3)`

Answer

To calculate the number of moles of \( \text{Na}_2\text{CO}_3 \) in 5.0 L of a 0.75 M solution, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Definition of Molarity**:
Molarity (M) is defined as the number of moles of solute (in this case, \( \text{Na}_2\text{CO}_3 \)) per liter of solution. The formula for molarity is:
\[ \text{Molarity (M)} = \frac{\text{Number of moles of solute}}{\text{Volume of solution in liters}} \]

2. **Identify the Given Values**:
- Volume of the solution = 5.0 L
- Molarity of the solution = 0.75 M

3. **Use the Molarity Formula to Find the Number of Moles**:
Rearranging the molarity formula to find the number of moles:
\[ \text{Number of moles} = \text{Molarity} \times \text{Volume of solution} \]
Substituting the known values:
\[ \text{Number of moles} = 0.75 \, \text{M} \times 5.0 \, \text{L} \]

4. **Perform the Calculation**:
\[ \text{Number of moles} = 0.75 \times 5.0 = 3.75 \, \text{moles} \]

5. **Conclusion**:
Therefore, the number of moles of \( \text{Na}_2\text{CO}_3 \) in 5.0 L of a 0.75 M solution is **3.75 moles**.