3.4 - Using Concentrations Of Solutions In mol

Write down the two formulae that link concentration, mole/mass, and volume together.

• concentration (g per dm³) = mass (g) ÷ volume (dm³)

• concentration (mol per dm³) = # of moles ÷ volume (dm³)

31.0 cm³ of potassium hydroxide solution neutralized 25.0 cm³ of 2.0 mol/dm^-3 nitric acid.

• HNO₃ + KOH → KNO₃ + H₂O

Calculate the concentration of the potassium hydroxide solution in mol/dm^-3.

• 2 × 0.025 dm³ (25 ÷ 1000 to convert the units) = 0.05 moles

• Ratio is 1:1 therefore number of moles of KOH = 0.05

• concentration = moles ÷ volume || 0.05 ÷ 0.031 = 1.61

When can you calculate the concentration of a substance?

If the volumes of two solutions that react completely are known and the concentration of one solution is known.

How many cm³ are in 1 dm³?

1000