35 g of sodium chloride is dissolved in 100 g of water at 293 K. Find its concentration at this temperature.

Options

A. 20.45%
B. 25.9%
C. 41.45%
D. None of these

Explanation

To find the concentration of sodium chloride (NaCl) dissolved in water, we can follow these steps:

### Step 1: Identify the mass of the solute and solvent
- Mass of sodium chloride (solute) = 35 g
- Mass of water (solvent) = 100 g

### Step 2: Calculate the mass of the solution
The mass of the solution is the sum of the mass of the solute and the mass of the solvent:
\[ \text{Mass of solution} = \text{Mass of solute} + \text{Mass of solvent} \]
\[ \text{Mass of solution} = 35 \, \text{g} + 100 \, \text{g} = 135 \, \text{g} \]

### Step 3: Calculate the concentration
Concentration can be calculated using the formula:
\[ \text{Concentration} = \left( \frac{\text{Mass of solute}}{\text{Mass of solution}} \right) \times 100 \]
Substituting the values:
\[ \text{Concentration} = \left( \frac{35 \, \text{g}}{135 \, \text{g}} \right) \times 100 \]

### Step 4: Perform the calculation
Calculating the fraction:
\[ \frac{35}{135} \approx 0.2593 \]
Now, multiplying by 100 to get the percentage:
\[ \text{Concentration} \approx 0.2593 \times 100 \approx 25.93\% \]

### Final Answer
The concentration of sodium chloride in the solution is approximately **25.9%**.

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