Answer to Question #184634 in Chemistry for Angela Tariga

Question

What is the concentration if 40 g NaOH is dissolved in 1000g of water?

Answer 1

Solution:

The molar mass of NaOH is 40 g/mol.

Hence,

Moles of NaOH = (40 g NaOH) × (1 mol NaOH / 40 g NaOH) = 1 mol NaOH

Molality (m):

Molality of a solution is the moles of solute divided by the kilograms of solvent.

Molality of NaOH solution = Moles of NaOH / Kilograms of solvent

Mass of solvent (H₂O) = 1000 g = 1 kg

Hence,

Molality of NaOH solution = 1 mol / 1 kg = 1 mol/kg = 1 m

Thus, a solution made by dissolving 40 g NaOH in 1000 g H₂O is 1 molal.

Molarity (M):

Molarity of a solution is the number of moles of solute per liter of solution.

Molarity of NaOH solution = Moles of NaOH / Volume of solution

1000 g of water is equivalent to 1 L

Hence,

Molarity of NaOH solution = 1 mol / 1 L = 1 mol/L = 1 M

Thus, a solution made by dissolving 40 g NaOH in 1000 g H₂O is 1 molar.

Normality (N):

Normality of a solution is the gram equivalent weight of a solute per liter of solution.

Since, NaOH is monobasic acid its normality and molarity will be same.

Hence,

Normality of NaOH solution = 1 N

Thus, a solution made by dissolving 40 g NaOH in 1000 g H₂O is 1 normal.