Calculate the molarity

Question

Calculate the molarity of 0.700 mol of Na2S in 1.65 L of solution

Answer 1

Molarity, by definition is mols (of a substance or compound) / L (of the solvent). We can remember it more simply by just mols/Liter.

To find the molarity of a solution with 0.700 mol of Na₂S in 1.65 L of solution, you'd simply set up the equation to look like: 0.700 mol Na₂S / 1.65 L solution = ____ M Na₂S (where the capital M signifies molarity).

I hope that answers your question! If it does, perfect, if not, keep reading below and maybe the extra tidbit will help.

Extra information

Additionally, we can find the molarity of a single ion in solution. If we wanted to know the molarity of Na⁺ in our solution, we'd first have to find the number of mols of Na⁺ present by using the molecular formula. There are 2 sodium ions in every molecule of sodium sulfide. So, for every mol of sodium sulfide, we'd have TWO mols of sodium ions!

To find the molarity of sodium ions in this solution we'd set up an equation that looks like this:

(2 mols Na⁺ / 1 mol Na₂S) x 0.700 mol Na₂S / 1.65 L solution = _____ M Na⁺

Answer 2

Molarity is mole divided by liters (M = mol/L).

0.700/1.65 = 0.424 M Na2S with correct sig figs.