In a given sample of bleaching powder, the precentage of available chlorine is 49. The volume in litres of chlorine obtained if 20 g of the sample is treated with HCI at NTP is?

Explanation

To solve the problem, we need to determine the volume of chlorine gas produced when 20 g of bleaching powder is treated with hydrochloric acid (HCl) at normal temperature and pressure (NTP).

### Step-by-Step Solution:

1. **Identify the Available Chlorine in Bleaching Powder:**
- The percentage of available chlorine in the bleaching powder is given as 49%. This means that in every 100 g of bleaching powder, 49 g is available chlorine.

2. **Calculate the Mass of Available Chlorine in 20 g of Bleaching Powder:**
- To find the mass of available chlorine in 20 g of the sample:
\[ \text{Mass of available chlorine} = \left(\frac{49}{100}\right) \times 20 \text{ g} = 9.8 \text{ g} \]

3. **Determine the Number of Moles of Chlorine:**
- The molecular mass of chlorine (Cl2) is approximately 71 g/mol. To find the number of moles of chlorine:
\[ \text{Number of moles of Cl2} = \frac{\text{Mass of Cl2}}{\text{Molecular mass of Cl2}} = \frac{9.8 \text{ g}}{71 \text{ g/mol}} \approx 0.138 \text{ moles} \]

4. **Calculate the Volume of Chlorine Gas at NTP:**
- At NTP, 1 mole of any gas occupies 22.4 liters. Therefore, the volume of chlorine gas produced can be calculated as:
\[ \text{Volume of Cl2} = \text{Number of moles of Cl2} \times 22.4 \text{ L/mol} = 0.138 \text{ moles} \times 22.4 \text{ L/mol} \approx 3.09 \text{ L} \]

### Final Answer:
The volume of chlorine gas obtained when 20 g of the sample is treated with HCl at NTP is approximately **3.09 liters**.