Chemistry solubility

Question

What is the molarity of a solution made with 6.940 grams of NaOH and 500 Milliliters?

Answer 1

Molarity is equal to mols of solute divided by liters of solution, so we will need to convert the NaOH mass to moles and the volume in mL to L.

1. We determine the molar mass of NaOH:
2. Na: 22.99 x 1 = 22.99
3. O: 16.00 x 1 = 16.00
4. H: 1.01 x 1 = 1.01
5. add all the values up to get 40.00 g/mol as the molar mass of NaOH

1. We convert the mass to moles using the molar mass
2. 6.940 g NaOH * ( 1 mol NaOH / 40.00 g NaOH) = 6*1/40 = 0.1500 mol NaOH
3. note: we multiplied by the inverse of molar mass here so that the "g" unit would cancel out and our answer would have units of moles
4. We convert the volume to L using a standard conversion factor
5. 500 mL * (1 L / 1000 mL) = 500/1000 = 0.500 L
6. note: again, I oriented my conversion factor so that the "mL" units cancel out, leaving me with L as the unit of my answer
7. Plug both values into the molartiy equation: M = n/V
8. M = n/V = 0.1500 mol / 0.500 L = 0.300 M