What would be the molality of 10% (mass/mass) aqueous solution
of KI ? (molar mass of KI `= 166 g mol^(-1)`)

Options

A. `1.08`
B. `0.48`
C. `0.66`
D. `0.35`

Answer

To find the molality of a 10% (mass/mass) aqueous solution of KI, we will follow these steps:

### Step 1: Understand the mass percentage
The mass percentage of a solution indicates that there are 10 grams of solute (KI) in every 100 grams of the solution.

### Step 2: Determine the mass of the solute and solvent
From the 10% mass/mass solution:
- Mass of solute (KI) = 10 grams
- Mass of solution = 100 grams
- Therefore, mass of solvent (water) = Mass of solution - Mass of solute = 100 grams - 10 grams = 90 grams

### Step 3: Convert the mass of the solvent to kilograms
Since molality is defined as moles of solute per kilogram of solvent, we need to convert the mass of the solvent from grams to kilograms:
- Mass of solvent = 90 grams = 90/1000 = 0.090 kilograms

### Step 4: Calculate the moles of solute
To find the moles of KI, we use the formula:
\[ \text{Moles of KI} = \frac{\text{mass of KI}}{\text{molar mass of KI}} \]
Given that the molar mass of KI is 166 g/mol:
\[ \text{Moles of KI} = \frac{10 \text{ grams}}{166 \text{ g/mol}} \approx 0.06024 \text{ moles} \]

### Step 5: Calculate the molality
Now, we can calculate the molality (m) using the formula:
\[ \text{Molality (m)} = \frac{\text{moles of solute}}{\text{mass of solvent in kg}} \]
Substituting the values we have:
\[ \text{Molality} = \frac{0.06024 \text{ moles}}{0.090 \text{ kg}} \approx 0.668 \text{ mol/kg} \]

### Step 6: Round off the answer
Rounding off the value, we can say that the molality of the solution is approximately 0.67 mol/kg.

### Final Answer
The molality of the 10% (mass/mass) aqueous solution of KI is approximately **0.67 mol/kg**.

---