PASSAGE-I :A mole of an atom is a collection of atoms whose total mass is the number of grams equal to the atomic mass. Since equal number of moles of different elements contain an equal number of atoms it becomes convenient to express the amounts of the elements in terms of moles. A mole represents a definite number of particles viz, atoms, molecules, ions or electrons. This definite number is called Avogadro number or Avogadro constant which is equal to `6.022 xx 10^(23)` Hence a mole represents `6.022 xx 10^(23)` particles of the substance. One mole of substance represents one gram-formula of the substance. One mole of a gas at standard temperature and pressure occupies 22.4 litres.
How many number of moles are there in 5.75 g of sodium ? (Atomic mass of sodium = 23)

Options

A. 0.25
B. 0.5
C. 1
D. 2.5

Explanation

To find the number of moles in 5.75 g of sodium, we can use the formula:

\[ \text{Number of moles} = \frac{\text{Mass of substance (g)}}{\text{Molar mass (g/mol)}} \]

### Step-by-step Solution:

1. **Identify the given values**:
- Mass of sodium = 5.75 g
- Atomic mass (molar mass) of sodium = 23 g/mol

2. **Substitute the values into the formula**:
\[ \text{Number of moles} = \frac{5.75 \, \text{g}}{23 \, \text{g/mol}} \]

3. **Perform the calculation**:
- Calculate the division:
\[ \text{Number of moles} = \frac{5.75}{23} \approx 0.25 \, \text{moles} \]

4. **Conclusion**:
- Therefore, the number of moles in 5.75 g of sodium is approximately 0.25 moles.