A mole is a collection of `6.022 xx 10^23` particles and the number `6.022 xx 10^23` is called Avogadro number. The mass of this number of atoms in an element is equal to its gram atomic mass and mass of this number of molecules in a compound is equal to its gram molecular mass. The volume occupied by this number of molecules of a gas at N.T.P is 22.4 L. When `6.022 xx 10^23` molecules of a substance are dissolved in 1L of solution, the solution is known as 1 molar volume.
The mass of 10 molecules of naphthalene `(C_(10)H_(8))`

Options

A. `2.12 xx 10^(22)`g
B. `2.12 xx 10^(21)`g
C. `2.12 xx 10^(23)` g
D. 1280 g

Explanation

To find the mass of 10 molecules of naphthalene (C₁₀H₈), we can follow these steps:

### Step 1: Calculate the molar mass of naphthalene (C₁₀H₈)
- The molecular formula of naphthalene is C₁₀H₈.
- The molar mass can be calculated as follows:
- Carbon (C) has an atomic mass of approximately 12 g/mol.
- Hydrogen (H) has an atomic mass of approximately 1 g/mol.

\[ \text{Molar mass of C}_{10}\text{H}_{8} = (10 \times 12) + (8 \times 1) = 120 + 8 = 128 \text{ g/mol} \]

### Step 2: Relate the molar mass to the number of molecules
- We know that 1 mole of naphthalene contains \(6.022 \times 10^{23}\) molecules and has a mass of 128 grams.

### Step 3: Calculate the mass of one molecule of naphthalene
- The mass of one molecule can be calculated by dividing the molar mass by Avogadro's number:

\[ \text{Mass of one molecule} = \frac{128 \text{ g}}{6.022 \times 10^{23}} \approx 2.12 \times 10^{-22} \text{ g} \]

### Step 4: Calculate the mass of 10 molecules of naphthalene
- To find the mass of 10 molecules, multiply the mass of one molecule by 10:

\[ \text{Mass of 10 molecules} = 10 \times \left(\frac{128 \text{ g}}{6.022 \times 10^{23}}\right) = \frac{1280 \text{ g}}{6.022 \times 10^{23}} \approx 2.12 \times 10^{-21} \text{ g} \]

### Conclusion
- The mass of 10 molecules of naphthalene is approximately \(2.12 \times 10^{-21}\) grams.