Question

Assuming that the concentration of sodium hypochlorite is 4.0% (w/v), calculate the molarity of the sodium hypochlorite solution. molar mass of sodium hypochlorite = 74.44g/mol.

Answer 1

We are told that the concentration of sodium hypochlorite is 4.0% (w/v). To calculate the molarity of the sodium hypochlorite solution, let us consider a sample volume of 0.1 liter. Since we are given a w/v (Percent of weight of solution in the total volume of solution) value, it means that there are 4 grams of sodium hypochlorite per 100 mL of solution (0.1 liter). Molarity is measured in moles per liter. So we'll just convert the given 4 grams to moles using the molar mass.

4 gramssodium hypochlorite * (1 mol sodium hypochlorite/ 74.44 g sodium hypochlorite) = 0.054 moles sodium hypochlorite

So we have 0.054 moles sodium hypochlorite  / 0.1 L solution

Thus the molarity is 0.53 mol/L or just 0.53 M.