Mole calculations in solutions - higher tier
You can calculate the number of The amount of substance that contains the same number of particles as there are atoms in 12 g of carbon-12 (contains the Avogadro's constant 6.0 Ă10ÂČÂł number of particles). of a substance in solution if you know the volume and the concentration. You can also work out the concentration of an Substance which produces hydrogen ions when dissolved in water. reacting with an A base which is soluble in water. and vice versa.
\(concentration~in~mol/dm^3 = \frac{moles}{volume~in~dm^3}\)
This equation can be rearranged to find the number of moles of Is the substance that dissolves in a solvent. or volume of A solute dissolved in a solvent..
Divide volumes in cm3 by 1000 to convert it into dm3.
Calculating concentration
Question
0.5 mol of solute is dissolved in 250 cm3 of solution. Calculate its concentration.
250 cm3 = 250 Ă· 1000 = 0.25 dm3
Concentration = 0.5 Ă· 0.25 = 2.0 mol/dm3
Calculating amount of solute
Rearranging the equation: amount = concentration Ă volume
Question
Calculate the amount of solute dissolved in 2 dm3 of a 0.1 mol/dm3 solution.
Amount = 0.1 Ă 2 = 0.2 mol
Calculating volume
Rearranging the equation: volume = amount Ă· concentration
Question
Calculate the volume of a 2 mol/dm3 solution that contains 0.5 mol of solute.
Volume = 0.5 Ă· 2 = 0.25 dm3
Note that 0.25 dm3 is the same as 250 cm3 (0.25 Ă 1000).
Concentrations are also expressed in grams per cubic decimeter (g/dm3). Use theThe relative formula mass (Mr) of a compound is calculated by adding together the relative atomic masses (Ar) of the atoms present in the compound. (Mr) to convert the two units of concentration.