Bleaching power is a mixed salt of hydrochloric acid and hypochlorious acid. It has the formula, `CaOCI_(2).H_(2)O`. It is manuafactured by the action of chlorine on dry slaked lime at `40^(@)C`. There is also a view that bleaching power is a mixture `[Ca(OCI)_(2)+CaCI_(2).Ca(OH)_(2).H_(2)O]`. The amount of chlorine obtained form a sample of bleching power by the treatement with excess of dilute acids or `CO_(2)` is called a available chlorine. A good sample of bleaching power constains `35-38%` of available chlorine. On long standing, it undergoes auto-oxidation and the amount of acvailable chlorine decreases. The estimation of available chlorine is done volumetrically by (a) iodometric method or by (b) aresenite method. In textile industry, the cotton cloth is mainly bleached with the help of bleaching power.
`3.55` g of bleachig power when treated with acetic acid and excess of KI liberated iodine which required 60 mL of `0.5` N sodium thiosulphate solution. The percentage of available chlorine in the sample is

Options

A. `30.0`
B. `25.0`
C. `20.0`
D. `35.0`

Explanation

To find the percentage of available chlorine in the sample of bleaching powder, we can follow these steps:

### Step 1: Calculate the number of equivalents of chlorine
We know that the liberated iodine requires 60 mL of 0.5 N sodium thiosulfate solution. Since the reaction between chlorine (Cl₂) and sodium thiosulfate is equivalent to that of iodine (I₂), we can say that the number of equivalents of chlorine is equal to the number of equivalents of iodine.

Using the formula for equivalents:
\[ \text{Number of equivalents} = \text{Normality} \times \text{Volume (in L)} \]
We convert the volume from mL to L:
\[ 60 \, \text{mL} = 60 \times 10^{-3} \, \text{L} = 0.060 \, \text{L} \]
Now we can calculate the number of equivalents of chlorine:
\[ \text{Number of equivalents of Cl}_2 = 0.5 \, \text{N} \times 0.060 \, \text{L} = 0.030 \, \text{equivalents} \]

### Step 2: Calculate the mass of chlorine
The equivalent weight of chlorine (Cl₂) is 35.5 g (for Cl, it's 35.5 g/mol, and since Cl₂ has two Cl atoms, the equivalent weight is half of the molar mass).

Now we can calculate the mass of chlorine:
\[ \text{Mass of Cl}_2 = \text{Number of equivalents} \times \text{Equivalent weight} \]
\[ \text{Mass of Cl}_2 = 0.030 \, \text{equivalents} \times 35.5 \, \text{g/equivalent} = 1.065 \, \text{g} \]

### Step 3: Calculate the percentage of available chlorine
To find the percentage of available chlorine in the bleaching powder sample, we use the formula:
\[ \text{Percentage of available chlorine} = \left( \frac{\text{Mass of Cl}_2}{\text{Mass of bleaching powder}} \right) \times 100 \]
Substituting the values we have:
\[ \text{Percentage of available chlorine} = \left( \frac{1.065 \, \text{g}}{3.55 \, \text{g}} \right) \times 100 \approx 30\% \]

### Conclusion
Thus, the percentage of available chlorine in the sample of bleaching powder is **30%**.

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