Practical 1

• What is the purpose of titration in chemistry?

  To determine the concentration of a solution
• How do you determine the end point in a titration?

  Add indicator until color change occurs
• What types of reactions are commonly used in titrations?

  Neutralisation and redox reactions
• In the phrase "titrate solution A with solution B," where should A be placed?

  In the conical flask
• How is the substance with unknown concentration measured?

  Using a volumetric pipette
• What is the first step in the titration method using a pipette?

  Rinse the pipette with the substance
• How should the bottom of the meniscus be positioned in the burette?

  On the marked line on the neck
• Why is a conical flask preferred over a beaker for titrations?

  It is easier to swirl without spilling
• What should be done to the burette before use?

  Rinse it with the solution to be added
• What happens if the burette is not rinsed properly?

  It may dilute the added solution
• Why should the funnel not be left in the burette during titration?

  It may cause false burette readings
• How should the burette readings be recorded?

  To 2 decimal places 0.00 or 0.05
• What does a reading of 9.15 cm³ indicate on a burette?

  The meniscus is between 9.1 and 9.2
• What should be done with the solution from the burette during titration?

  Add dropwise while swirling the mixture
• What is the purpose of distilled water during titration?

  To wash the sides of the flask
• Why should only distilled water be used to wash conical flasks?

  It does not add extra moles of reagents
• What should be included when recording titration results?

  • Initial and final burette readings
  • Titre volumes to 2 decimal places
  • Clearly recorded in a table
• Why is it important to repeat titrations?

  To spot and discount anomalous titres
• How do you calculate percentage error for apparatus?

  % uncertainty = (uncertainty / measurement) x 100
• How do you find the maximum total percentage apparatus uncertainty?

  Add all individual equipment uncertainties together
• How can you decrease apparatus uncertainties?

  Use apparatus with greater resolution
• Why is it important to fill the space below the tap in the burette with sodium hydroxide?

  To ensure accurate titration volume
• How does rinsing the conical flask with deionised water improve accuracy?

  It ensures no contaminants affect the reaction
• Why does repeating a titration make the average titre more reliable?

  It reduces random errors in measurements
• How would using too much phenolphthalein affect the average titre?

  It would likely increase the average titre
• What is the effect of adding too much water to the volumetric flask?

  It dilutes the acid, lowering concentration
• Write a method to make up a standard solution

  1. Weigh out an accurate mass of solid on a weighing boat
  2. Tip the solute into a volumetric flask and reweigh the boat to get the mass of solute
  3. Water is added and the flask shaken to dissolve the solute
  4. Once dissolved flask is made up to 250 cm3 and inverted to mix thoroughly with stopper
• What is a standard solution?

  A solution with a known mass of solute dissolved in a known volume of solution
• Write a method for a simple acid-base titration

  1. Rinse the burette with the solution you are going to fill it with, discard and fill the burette
  2. Rinse the pipette with the solution you are going to pipette into conical flask, transfer 25.0 cm3 of solution to be analysed
  3. Add 2-3 drops of suitable indicator to the conical flask
  4. Add solution from the burette with constant swirling until indicator just changes colour, adding drop wise near the end point
  5. Repeat the titration until 2-3 concordant results achieved
  6. Calculate the mean titre from the concordant results
• What does it mean by concordant results?

  Results that are consistent and within 0.10 cm3 of one another
• What should the conical flask be washed with?

  Water and not the solution going into it as there would be more moles of that substance in flask than we think we have