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.
What is the mass in grams of a single atom of chlorine? (Atomic mass of chlorine = 35.5)

Options

A. `6.54 xx 10^(23) g`
B. `5.9 xx 10^(-23)` g
C. 0.0025 g
D. 35.5 g

Explanation

To find the mass in grams of a single atom of chlorine, we can follow these steps:

### Step 1: Understand the relationship between moles and atomic mass
The atomic mass of chlorine is given as 35.5 grams per mole. This means that one mole of chlorine atoms (which contains Avogadro's number of atoms) has a mass of 35.5 grams.

### Step 2: Use Avogadro's number
Avogadro's number is \(6.022 \times 10^{23}\), which represents the number of atoms in one mole of a substance.

### Step 3: Calculate the mass of a single atom
To find the mass of a single atom of chlorine, we can use the unitary method:
\[ \text{Mass of one atom} = \frac{\text{Mass of one mole}}{\text{Avogadro's number}} \]
Substituting the values:
\[ \text{Mass of one atom} = \frac{35.5 \text{ grams}}{6.022 \times 10^{23} \text{ atoms}} \]

### Step 4: Perform the calculation
Now, we perform the division:
\[ \text{Mass of one atom} = \frac{35.5}{6.022 \times 10^{23}} \approx 5.9 \times 10^{-23} \text{ grams} \]

### Conclusion
Thus, the mass of a single atom of chlorine is approximately \(5.9 \times 10^{-23}\) grams.

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