Calculate Concentration - 1

Concentration calculations use one equation, rearranged three ways:amount (mol) = concentration (mol dm^-3) × volume (dm³)so concentration = amount ÷ volume, and volume = amount ÷ concentration.The volume must be in dm³. Laboratory volumes are usually measured in cm³, so divide by 1000 first: 25.0 cm³ = 0.0250 dm³. Forgetting this step gives an answer 1000 times too big or too small.Worked example 1 (finding moles): how many moles of sodium hydroxide are in 25.0 cm³ of 0.100 mol dm^-3 solution?amount = 0.100 × (25.0 ÷ 1000) = 2.50 × 10^-3 molWorked example 2 (finding concentration): 0.0500 mol of a solute is dissolved in water and made up to 250 cm³. What is the concentration?concentration = 0.0500 ÷ 0.250 = 0.200 mol dm^-3Worked example 3 (finding volume): what volume of 0.500 mol dm^-3 acid contains 0.0100 mol?volume = 0.0100 ÷ 0.500 = 0.0200 dm³ = 20.0 cm³A quick sense check helps: a dilute solution (small concentration) in a small volume must contain only a small number of moles.