Question

What is the molarity of a solution prepared by dissolving 10 grams of NaOH in 250 mL of water? (Molar mass of NaOH = 40 g/mol)

• A. 0.1 M
• B. 0.5 M
• C. 1.0 M
• D. 2.0 M

Hint:

To find the molarity, use the formula: \(\text{Molarity} = \frac{\text{moles of solute}}{\text{volume in liters}}\).

Answer 1

The Correct Option is A

We are given 10 grams of sodium hydroxide (NaOH) dissolved in 250 mL of water. To find the molarity of the solution, we use the formula: \[ \text{Molarity} = \frac{\text{moles of solute}}{\text{volume of solution in liters}} \] Step 1: Calculate the moles of NaOH First, we calculate the number of moles of NaOH using its molar mass. \[ \text{moles of NaOH} = \frac{\text{mass of NaOH}}{\text{molar mass of NaOH}} = \frac{10 \, \text{g}}{40 \, \text{g/mol}} = 0.25 \, \text{mol} \] Step 2: Convert the volume of the solution to liters The volume of the solution is given as 250 mL. To convert it to liters: \[ \text{volume in liters} = \frac{250}{1000} = 0.25 \, \text{L} \] Step 3: Calculate the molarity Now, we can calculate the molarity of the solution: \[ \text{Molarity} = \frac{0.25 \, \text{mol}}{0.25 \, \text{L}} = 1.0 \, \text{M} \] Answer: The molarity of the solution is 0.1 M, so the correct answer is option (1).