Find molarity of 10 g NaOH in 200 ml of water.

CONCEPT:

Molarity (M)

• Molarity is a measure of the concentration of a solute in a solution, or of any chemical species in terms of amount of substance in a given volume. It is defined as the number of moles of solute divided by the volume of the solution in liters.
• The formula for molarity is:

  M = $\frac{\text{moles of solute}}{\text{liters of solution}}$

EXPLANATION:

• First, calculate the moles of NaOH:
  • Molecular weight of NaOH = 23 (Na) + 16 (O) + 1 (H) = 40 g/mol
  • Moles of NaOH = $\frac{\text{mass}}{\text{molecular weight}}$
  • = $\frac{10 \text{ g}}{40 \text{ g/mol}}$
  • = 0.25 mol
• Next, convert the volume of the solution from milliliters to liters:
  • Volume = 200 ml = 200/1000 = 0.2 L
• Finally, calculate the molarity:
  • M = $\frac{\text{moles of solute}}{\text{liters of solution}}$
  • = $\frac{0.25 \text{ mol}}{0.2 \text{ L}}$
  • = 1.25 M

Therefore, the molarity of 10 g NaOH in 200 ml of water is 1.25 M.