Using the Mole The mole is a conversion factor used in chemistry– this shows you how this is extended.Volume X 24 dm3 X 6 x 1023 Numberof a gas Moles of ÷ 24 dm3 (dm3) ÷ 6 x 1023 particles x formula ÷ mass formula mass Key fact – always Mass (g) multiply when working out of the mole box!
Concentration of a solutionA solution contains dissolved particles (the solute) in a solvent (the liquid).The concentration refers to the amount of dissolved solute in the solution.
Volume of solutionThe volume of a solution is measured in cm3 or dm3.Recall that: 1dm3 = 1000cm3.The volume of a solution is measured using: (a) Measuring cylinder (b) burette (c) pipette (d) standard flask
Formula for concentrationThe formula for concentration is:Concentration = number of moles ÷ volumeConcentration = mass ÷ volumeConcentration can be measured in: (a) moles/dm3 (b) grams/dm3
Calculations using concentration.Recall this triangle: n C V
Example(1) Calculate the concentration of a solution which has 160g of sodium hydroxide (NaOH) in 2dm3 solution.(2) Calculate the number of moles of sodium hydroxide in 500cm3 of the above sodium chloride solution.(3) Calculate the volume of this solution which will contain 0.1 moles of sodium hydroxide.
Diluting solutionsThe rule is: multiply the starting volume by the number of times the solution is to be dilutes and subtract the starting volume.So to dilute 20cm3 of 1mol/dm3 solution to 0.1mol/dm3:Add (1/0.1 x 20) – 20 = 180cm 3 water