Experimental Techniques

A list of the experimental techniques and how to carry them out requried for F334 and F335 exams. 

HideShow resource information
  • Created by: Adele
  • Created on: 24-05-14 14:51

Using a Colorimeter

Colorimetry

  • Select a filter with the complementary colour to the solution being tested. 
  • Zero the colorimeter (calibrate it) using a cuvette of distilled water
  • Make up solutions of known concentrations both above and below that of the unknown sample.
  • Measure the absorbance of each concentration and plot a calibration curve of the results. (absorbance against concentration) 
  • Measure the absorbance of the unknown soluton and read off the concentration from the calibration curve once results have been plotted. 
1 of 5

Thin-layer Chromatography

T.L.C.

  • Spot mixtures and reference samples on a pencil line 1cm from the bottom of the T.L.C. plate. 
  • Place T.L.C. plate in beaker containing solvent. Solvent level must be below 1cm base line. Cover beaker. 
  • Remove plate when solvent is near top and mark how far it reached. 
  • Allow plate to dry. Locate spots using a locating agent such as iodine or ninhydrin. 
  • Find Rf values for each spot and compare these to reference sample Rf values to decide what the unknown is. 
2 of 5

Recrystallisation

Recrystallisation

  • Dissolve solid in a minumum volume of hot solvent. 
  • Filter and retain the filtrate. 
  • Allow filtrate to cool, which will form crystals.
  • Collect the crystals using vaccum filtration and wash them in a minimum volume of cold solvent.
  • Dry in an oven set below the melting point of the crystals. 
3 of 5

Redox Titrations

Potassium manganate (VII) Titration: Used to find the concentration of iron(II) ions or hydrogen peroxide

  • Use a pipette to transfer a known volume of the test solution (iron(II) ions for example) into a conical flask. 
  • Acidify this solution with dilute sulfuric acid. 
  • Slowly add potassium manganate(VII) to the solution in the conical flask from a burette.
  • Swirl gently until a pale pink colour persists.
  • Repeat the titration until you have two titres within 0.1cm^3.
4 of 5

Redox Titrations

Iodine-Thiosulfate Titrations: Used to find the concentrations of solutions of oxidising agents

  • A known amount of the oxidising agent is reacted with an excess of acidified potassium iodide solution. 
  • The iodine produced is then titrated against a standard solution of sodium thiosulfate. 
  • Near the end point of the reaction, a few drops of starch solution are added giving an intense blue/black colour which disappears at the end point. 


5 of 5

Comments

No comments have yet been made

Similar Chemistry resources:

See all Chemistry resources »See all Experimental Techniques resources »