4) How many grams of NaCl must be added to 2.00 mL of water to make a 85.5 M solution? \( (1000 \mathrm{~mL}=1 \mathrm{~L}) \)

To determine how many grams of NaCl (sodium chloride) are needed to make an 85.5 M (molar) solution in 2.00 mL of water, follow these steps: ### Step 1: Convert Volume from mL to L \[ 2.00 \, \text{mL} = 0.002 \, \text{L} \] ### Step 2: Calculate Moles of NaCl Required The molarity (M) is given by: \[ M = \frac{\text{moles of solute}}{\text{volume of solution in liters}} \] Rearranging to find moles: \[ \text{moles of NaCl} = M \times \text{volume} = 85.5 \, \text{M} \times 0.002 \, \text{L} = 0.171 \, \text{moles} \] ### Step 3: Calculate Mass of NaCl First, find the molar mass of NaCl: \[ \text{Na} = 22.99 \, \text{g/mol} \] \[ \text{Cl} = 35.45 \, \text{g/mol} \] \[ \text{Molar mass of NaCl} = 22.99 + 35.45 = 58.44 \, \text{g/mol} \] Now, calculate the mass: \[ \text{Mass} = \text{moles} \times \text{molar mass} = 0.171 \, \text{moles} \times 58.44 \, \text{g/mol} \approx 10.0 \, \text{g} \] ### Final Answer **Approximately 10.0 g of NaCl must be added to make the solution.**