Question

5.85 g of NaCl is dissolved in 200 ml water. Calculate the molarity of the solution. [Na = 23, Cl = 35.5]

Hint:

Always remember: Molarity = \(\dfrac{\text{Moles of solute}}{\text{Liters of solution}}\). Convert ml to liters carefully to avoid errors.

Answer 1

Step 1: Calculate molar mass of NaCl.
Molar mass of NaCl = Atomic mass of Na + Atomic mass of Cl
= 23 + 35.5 = 58.5 g/mol
Step 2: Calculate moles of NaCl.
Moles of NaCl = \(\dfrac{\text{Given mass}}{\text{Molar mass}}\)
= \(\dfrac{5.85}{58.5} = 0.1 \, \text{mol}\)
Step 3: Convert volume of solution to liters.
200 ml = \(\dfrac{200}{1000} = 0.2 \, \text{L}\)
Step 4: Calculate molarity.
Molarity \(M = \dfrac{\text{Moles of solute}}{\text{Volume of solution in L}}\)
= \(\dfrac{0.1}{0.2} = 0.5 \, M\) Final Answer: \[ \boxed{0.5 \, M} \]