A 100ml soulution contains 8g of NaOH ( molecular weight 40g/mole). What is the concentration of this solution in g% and molarity?

Answer 1

First we need to find the number of moles of NaOH in this solution. You already presented the molecular weight and the mass of NaOH given, so this will be straightforward:

8g NaOH * (1 mole NaOH / 40g NaOH) = 0.2 moles of NaOH

Ok, we have the number of moles of NaOH. Now we need to find concentration in molarity. The units of molarity are: moles of solute per liter of solution. 100mL of solution is equal to 0.1 L.

0.2 moles NaOH / 0.1 L = 2M NaOH

To find g% concentration, you just take the mass of NaOH in grams and divide it by the total solution mass in grams. Assume that this is an aqueous based solution, so the density of solution is roughly 1g/mL.

100 mL * 1g/mL = 100g of solution total.

8g NaOH / 100g solution = 0.08 NaOH = 8% NaOH