Calculate the mass of sodium which contains same number of atoms as are present in 15 g of calcium (at. mass of Ca = 40, Na = 23).

Explanation

To solve the problem of calculating the mass of sodium (Na) that contains the same number of atoms as are present in 15 g of calcium (Ca), we will follow these steps:

### Step 1: Calculate the number of moles of calcium (Ca)
We start by using the formula for moles:
\[ \text{Number of moles} = \frac{\text{mass}}{\text{molar mass}} \]
Given:
- Mass of calcium = 15 g
- Atomic mass of calcium (Ca) = 40 g/mol

Now, we can calculate the number of moles of calcium:
\[ \text{Number of moles of Ca} = \frac{15 \text{ g}}{40 \text{ g/mol}} = 0.375 \text{ moles} \]

### Step 2: Calculate the number of atoms in calcium
Using Avogadro's number (\(6.022 \times 10^{23}\) atoms/mol), we can find the number of atoms in 0.375 moles of calcium:
\[ \text{Number of atoms of Ca} = 0.375 \text{ moles} \times 6.022 \times 10^{23} \text{ atoms/mole} \]
This calculation gives us the total number of atoms in the sample of calcium.

### Step 3: Find the number of moles of sodium (Na) that contains the same number of atoms
Since we want to find the mass of sodium that contains the same number of atoms as in 0.375 moles of calcium, we will also have 0.375 moles of sodium.

### Step 4: Calculate the mass of sodium (Na)
Using the formula for mass:
\[ \text{Mass} = \text{Number of moles} \times \text{Molar mass} \]
Given:
- Atomic mass of sodium (Na) = 23 g/mol

Now, we can calculate the mass of sodium:
\[ \text{Mass of Na} = 0.375 \text{ moles} \times 23 \text{ g/mol} = 8.625 \text{ g} \]

### Final Answer
The mass of sodium that contains the same number of atoms as are present in 15 g of calcium is **8.625 g**.

---