Practical Methods
Cards (7)
- determining rates of reaction
- indicate which substance is being measured and why
- state that a range of concentrations of the reactant are investigated
- state how the results are interpreted
- methods of measuring rate
- Colorimetry
- Titration
- pH change
- Gas evolution
- Conductivity
- measuring volume of gas produced over time --> rate>1 gas product, 0 gas reactants
- attach gas syringe to sealed conical flask (or collect over water in inverted measuring cylinder)
- start reaction
- measure gas volume produced at different time intervals
- repeat with different [reactant] concentrations
- plot volume/time graph and measure tangent t=0 to get rate
- plot rate against [reactant]
- colorimeter --> rate
- prepare range of samples, different conc of required solutions
- calibrate using appropriate filter and blank solution
- record absorbance/transmission of each solution of KNOWN conc
- draw calibration curve of a/t against time
- place REACTION MIXTURE in colorimeter and record a/t at different times
- use calibration curve to convert a/t to conc, plot graph of conc/time
- gradient of tangent at any conc gives rate, at that conc
- pH --> rate
- start reaction
- measure pH of solution at different time intervals, pH meter
- repeat with different conc of reagent
- calculate [H+] conc using pH = -log10[H+]
- plot [H+] against time and measure gradients of tangents at various [H+] to determine rate
- conductivity --> rate
- measure electrical conductivity of solution with time
- repeat with different conc of reagent
- plot conductivity against time and measure tangent at t=0
- plot rate against reagent conc
- Titration --> rate
- mix solutions, start reaction
- use pipette to take samples at regular time intervals
- quench sample (rapid cooling/add large vol of water/add chemical to remove reactant/p)
- titrate against standard -named acid/alkali- to find conc of -r/p- using -named indicator-
- plot conc -r/p- against time, grad of tangent at conc is rate at that conc