1. Given data

   • Volume of solution: $250\,\text{mL} = 0.250\,\text{L}$
   • Molarity: $0.35\,\text{M}$
   • Molar mass of $\mathrm{CH_3COONa}$: $82.02\,\text{g mol}^{-1}$

2. Use molarity formula $M = \frac{n}{V}$ So, number of moles required: $n = M \times V = 0.35 \times 0.250 = 0.0875\,\text{mol}$

3. Convert moles to mass $\text{mass} = n \times \text{molar mass}$ $\text{mass} = 0.0875 \times 82.02$ $\text{mass} = 7.17675\,\text{g}$

4. Final answer Required mass of sodium acetate is approximately $7.18\,\text{g}$

Since this is an integer-type question, the answer is taken as: $\boxed{7}$