Question

What is the volume of solution needed to prepare a 3 Molarity (M) solution containing 80 g of NaOH?

• A. 1.50 L / 1500 mL
• B. 1.33 L / 1330 mL
• C. 0.67 L / 667 mL
• D. 0.50 L / 500 mL

Hint:

To calculate the volume of solution needed for a given molarity, always use the molarity formula $M = \frac{\text{moles}}{V}$ and convert mass to moles using the molar mass.

Answer 1

The Correct Option is C

Step 1: Use the formula for molarity
The formula for molarity (M) is given by: $$ M = \frac{\text{moles of solute}}{\text{volume of solution in liters}} $$ Step 2: Calculate the moles of NaOH
The molar mass of NaOH is: $$ \text{Molar mass of NaOH} = 23 + 16 + 1 = 40 \, \text{g/mol} $$ So, the number of moles of NaOH in 80 g is: $$ \text{moles of NaOH} = \frac{80 \, \text{g}}{40 \, \text{g/mol}} = 2 \, \text{moles} $$ Step 3: Use the molarity formula to find the volume
Substitute the given values into the molarity formula: $$ 3 \, \text{M} = \frac{2 \, \text{moles}}{V} $$ Solving for $V$: $$ V = \frac{2 \, \text{moles}}{3 \, \text{M}} = 0.6667 \, \text{L} = 0.67 \, \text{L} = 667 \, \text{mL} $$ Step 4: Conclusion
The volume of solution needed is 0.67 L (or 667 mL). $$ \boxed{0.67 \, \text{L} \, \text{or} \, 667 \, \text{mL} \, \text{is the required volume.}} $$