Question

What is the molarity of a solution prepared by dissolving \( 5.0 \, \text{g} \) of sodium chloride (\( \text{NaCl} \)) in \( 250 \, \text{mL} \) of water? (Molar mass of NaCl = \( 58.5 \, \text{g/mol} \))

• A. \( 0.34 \, \text{M} \)
• B. \( 0.50 \, \text{M} \)
• C. \( 1.0 \, \text{M} \)
• D. \( 2.0 \, \text{M} \)

Hint:

To calculate the molarity of a solution, divide the moles of solute by the volume of the solution in liters. Make sure to convert mass to moles using the molar mass of the solute.

Answer 1

The Correct Option is A

The molarity \( M \) of a solution is calculated using the formula: \[ M = \frac{\text{moles of solute}}{\text{volume of solution in liters}} \] First, calculate the moles of sodium chloride (\( \text{NaCl} \)): \[ \text{moles of NaCl} = \frac{\text{mass of NaCl}}{\text{molar mass of NaCl}} = \frac{5.0 \, \text{g}}{58.5 \, \text{g/mol}} \approx 0.0855 \, \text{mol} \] Next, convert the volume of the solution from milliliters to liters: \[ \text{volume of solution} = 250 \, \text{mL} = 0.250 \, \text{L} \] Now, calculate the molarity: \[ M = \frac{0.0855 \, \text{mol}}{0.250 \, \text{L}} = 0.342 \, \text{M} \] Rounding to two decimal places, the molarity is \( 0.34 \, \text{M} \). Thus, the molarity of the solution is \( 0.34 \, \text{M} \).