How much mass of sodium acetate is required to make 240 mL of 0.575 molar aqueous solution?

Options

A. 11.5g
B. 10.5g
C. 15g
D. 13.5g

Explanation

To find out how much mass of sodium acetate is required to make a 240 mL of a 0.575 molar aqueous solution, we can follow these steps:

### Step 1: Write down the formula for molarity.
Molarity (M) is defined as the number of moles of solute divided by the volume of solution in liters.

\[ M = \frac{\text{Number of moles of solute}}{\text{Volume of solution in liters}} \]

### Step 2: Convert the volume from mL to liters.
Given volume is 240 mL. To convert this to liters, we divide by 1000.

\[ \text{Volume in liters} = \frac{240 \, \text{mL}}{1000} = 0.240 \, \text{L} \]

### Step 3: Calculate the number of moles of sodium acetate needed.
Using the molarity formula, we can rearrange it to find the number of moles:

\[ \text{Number of moles} = M \times \text{Volume in liters} \]

Substituting the values:

\[ \text{Number of moles} = 0.575 \, \text{mol/L} \times 0.240 \, \text{L} = 0.138 \, \text{mol} \]

### Step 4: Find the molar mass of sodium acetate.
The molar mass of sodium acetate (C₂H₃O₂Na) is given as 82 g/mol.

### Step 5: Calculate the mass of sodium acetate required.
Using the formula:

\[ \text{Mass} = \text{Number of moles} \times \text{Molar mass} \]

Substituting the values:

\[ \text{Mass} = 0.138 \, \text{mol} \times 82 \, \text{g/mol} = 11.316 \, \text{g} \]

### Step 6: Round the mass to the appropriate significant figures.
Since the given molarity (0.575) has three significant figures, we round the mass to three significant figures:

\[ \text{Mass} \approx 11.3 \, \text{g} \]

### Final Answer:
The mass of sodium acetate required is approximately **11.3 grams**.

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