1. **State the problem:** We need to prepare 100 mL of a solution containing 0.15 M NaCl, 5 mM MgCl2, and 0.5% sucrose using given stock solutions and solid sucrose. 2. **Formulas and rules:** - Use the dilution formula for each solute: $$C_1 \times V_1 = C_2 \times V_2$$ where $C_1$ and $V_1$ are concentration and volume of stock, $C_2$ and $V_2$ are desired concentration and final volume. - For sucrose, 0.5% means 0.5 g per 100 mL solution. 3. **Calculate volume of 5 M NaCl stock needed:** - Desired concentration $C_2 = 0.15$ M - Final volume $V_2 = 100$ mL - Stock concentration $C_1 = 5$ M $$V_1 = \frac{C_2 \times V_2}{C_1} = \frac{0.15 \times 100}{5} = \frac{15}{5} = 3 \text{ mL}$$ 4. **Calculate volume of 1 M MgCl2 stock needed:** - Desired concentration $C_2 = 5$ mM = 0.005 M - Final volume $V_2 = 100$ mL - Stock concentration $C_1 = 1$ M $$V_1 = \frac{0.005 \times 100}{1} = 0.5 \text{ mL}$$ 5. **Calculate mass of sucrose needed:** - 0.5% w/v means 0.5 g per 100 mL - So, mass = 0.5 g 6. **Summary of components:** - NaCl stock: 3 mL - MgCl2 stock: 0.5 mL - Sucrose solid: 0.5 g - Add distilled water to reach total volume 100 mL 7. **Prepare the solution:** - Add 3 mL of 5 M NaCl stock to a container. - Add 0.5 mL of 1 M MgCl2 stock. - Add 0.5 g of solid sucrose. - Add distilled water to bring total volume to 100 mL. This ensures the final solution has the desired concentrations and percent.