5g of a sample of bleaching powder is treated with excess acetic acid and KI solution. The liberated `I_(2)` required 50 mL of `N/10` hypo. The % of available chlorine in the sample.

Explanation

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

### Step 1: Write the reaction of bleaching powder with acetic acid and KI
Bleaching powder (Ca(OCl)₂) reacts with acetic acid (CH₃COOH) and potassium iodide (KI) to liberate iodine (I₂).

**Balanced Reaction:**
\[ \text{Ca(OCl)}_2 + 4 \text{CH}_3\text{COOH} + 2 \text{KI} \rightarrow \text{I}_2 + \text{CaCl}_2 + 4 \text{CH}_3\text{COOK} + 2 \text{H}_2\text{O} \]

### Step 2: Determine the moles of iodine liberated
The liberated iodine (I₂) reacts with sodium thiosulfate (hypo, Na₂S₂O₃). The reaction is as follows:

**Balanced Reaction:**
\[ \text{I}_2 + 2 \text{Na}_2\text{S}_2\text{O}_3 \rightarrow \text{Na}_2\text{S}_4\text{O}_6 + 2 \text{NaI} \]

### Step 3: Calculate the moles of sodium thiosulfate used
Given that 50 mL of N/10 (0.1 N) sodium thiosulfate is used, we can calculate the moles of Na₂S₂O₃:

\[ \text{Moles of Na}_2\text{S}_2\text{O}_3 = \text{Normality} \times \text{Volume (L)} = 0.1 \, \text{N} \times \frac{50}{1000} \, \text{L} = 0.005 \, \text{N} \]

### Step 4: Relate moles of iodine to moles of sodium thiosulfate
From the balanced equation, 1 mole of I₂ reacts with 2 moles of Na₂S₂O₃. Therefore, the moles of I₂ can be calculated as:

\[ \text{Moles of I}_2 = \frac{\text{Moles of Na}_2\text{S}_2\text{O}_3}{2} = \frac{0.005}{2} = 0.0025 \, \text{moles} \]

### Step 5: Calculate the mass of chlorine equivalent to the moles of I₂
Since 1 mole of I₂ corresponds to 2 moles of Cl₂, we can find the moles of Cl₂:

\[ \text{Moles of Cl}_2 = \text{Moles of I}_2 = 0.0025 \, \text{moles} \]

Now, the mass of chlorine (Cl) can be calculated using the molar mass of Cl (approximately 35.5 g/mol):

\[ \text{Mass of Cl} = \text{Moles of Cl}_2 \times \text{Molar mass of Cl} = 0.0025 \times 2 \times 35.5 \, \text{g} = 0.1775 \, \text{g} \]

### Step 6: Calculate the percentage of available chlorine in the sample
The percentage of available chlorine in the bleaching powder sample can be calculated as follows:

\[ \text{Percentage of available chlorine} = \left( \frac{\text{Mass of Cl}}{\text{Total mass of sample}} \right) \times 100 = \left( \frac{0.1775}{5} \right) \times 100 = 3.55\% \]

### Final Answer:
The percentage of available chlorine in the sample is **3.55%**.

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