Define: Rate of reaction
a measure of speed at which the concentration of products increases (or the concentration of reactants decreases)
Calc rate of reaction
(difference in [P]) / t OR (- difference [R]) / t
Techniques for determining a rate experimentally
Change in volume of gas produced/increase in gas pressure
- measure change in vol. of gas at regular time intervals
- use a gas syringe (or inverted burette) to observe/record volume directly
Techniques for determining a rate experimentally
Change in mass
- allows for continuous readings so that mass against time can be plotted
- works well for heavier gases
Techniques for determining a rate experimentally
Change in concentration measured using titration
- measure [react.] or [prod.] at certain time intervals by titrating against a “standard”
- since this technique involves a chemical reaction, it can’t be done continuously, takes “freeze” frames of the reaction instead
Techniques for determining a rate experimentally
Change in colour
- allows for continuous readings
- plot absorbance/transmittance against time
Techniques for determining a rate experimentally
Change in concentration measured using conductivity
- the decrease in [ions] will correspond to a decrease in electrical conductivity
Techniques for determining a rate experimentally
“Clock methods”
- sometimes when a reaction is complete, an observable change occurs
- this only gives an average rate over a certain time interval
