Question

What mass of calcium chloride, CaCl2, needs to be weighed to make a solution of volume 200cm^3 and concentration of 0.1 mol dm^-3

Answer 1

Answer:

The concentration of a solution can be shown in g/dm3 or mol/dm3. It is often more useful to know the concentration of a reactant in mol/dm3 so that the amount of reactant in a given volume can be calculated.

Concentration using moles

The concentration of a solution can be calculated using:

the amount of dissolved solute in moles, mol

the volume of solution (or solvent) in cubic decimetres, dm3

Example

0.5 mol of sodium hydroxide is dissolved in 2 dm3 of water. Calculate the concentration of the sodium hydroxide solution formed.

Concentration =

Concentration = 0.25 mol/dm3

Volume units

Volumes used in concentration calculations must be in dm3, not in cm3. It is useful to know that 1 dm3 = 1000 cm3. This means:

divide by 1000 to convert from cm3 to dm3

multiply by 1000 to convert from dm3 to cm3

For example, 250 cm3 is 0.25 dm3 (250 ÷ 1000). It is often easiest to convert from cm3 to dm3 before continuing with a concentration calculation.