ACIDS AND BASES 7.3 CONCENTRATION OF ACIDS AND ALKALIS

DEFINITION OF CONCENTRATION “Measurement which shows the quantity of a dissolved solute in 1 dm3 of the solution”

1 dm3 = 1000 cm3 Quantity of the dissolved solute is normally measured in gram or mol units. Two units used in the concentration of a solution. There are: g dm-3 mol dm-3

The formulae of solution concentration in g dm-3 = mass of solute (g) volume of solution (dm3)

The formulae of solution concentration in mol dm-3 = number of moles of solute (mol) volume of solution (dm3)

DEFINITION OF MOLARITY “The unit of concentration that shows the number of moles of a solute that dissolves in 1 dm3 of solution”

Relationship between number of moles with molarity and volume of a solution Number of moles = MV 1000 Where: M = molarity of solution (mol dm-3) V = volume of solution (cm3)

EXAMPLE 1: Question: Calculate the concentration in g dm-3 for 0.5 mol dm-3 of sodium hydroxide, NaOH, solution. (Relative atomic mass: H,1: O,16: Na,23)

EXAMPLE 2: Question: Calculate the molarity (concentration in mol dm-3) for 10g dm-3 of sodium hydroxide, NaOH solution. (Relative atomic mass: H,1: O,16: Na,23)