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Titrations
- A titration is used to measure accurately how much acid and alkali react completely together
- A pipette is used to accurately measure the volume of alkali put into a conical flask then an indicator is added to this
- In this chapter of IBDP Chemistry, a burette is filled with acid which is gradually added
- When the indicator changes colour the end point has been reached.
- The volume of acid used is found from the initial and final burette reading
- Titration should be done several times for more accurate and reliable results
Titration Calcuations
- Concentrations of solutions are measured in g/dm3 or mol/dm3
- In this chapter of IBDP Chemistry, if we know the mass or the number of moles of a substance dissolved in a given volume of solution we can calculate its concentration
- If we know the volume of a solution and its concentration we can calculate the mass or the number of moles of the substance in any volume of solution
- In this chapter of IBDP Chemistry, titrations are used to find the volumes of solutions that react exactly
- The concentrations are calculated using balanced symbol equations and moles
Worked example
A student found that 25.0cm3 of sodium hydroxide solution with an unknown concentration reacted with exactly 20.0cm3 of 0.50mol/dm3 hydrochloric acid. What was the concentration of the sodium hydroxide solution?
- The equation for this reaction is: NaOH(aq) + HCl(aq) → NaCl(aq) + H2O(l)
- The concentration of the HCl is 0.50mol/dm3, so 0.50mol of HCl are dissolved in 1000cm3 of acid.
- Therefore 20.0cm3 of acid contains 20 x 0.50/1000mol = 0.010mol HCl
- The equation for the reaction tells us that 0.010mol of HCl will react exactly with 0.010mol of NaOH.
- This means that there must be 0.010 moles of NaOH in the 25.0cm3 of solution in the conical flask.
- So, the concentration of NaOH solution = (0.010/25) x 1000 = 0.40mol/dm3
Titration Equation Calculations
This is the end of this topic.
