RP3 - Effect of temperature on rate of a reaction Flashcards
How can rate of reaction be measured?
● Initial rates method- i.e. the iodine clock reaction.
● A continuous monitoring method- i.e. measuring the volume of gas released in a reaction over time.
Why does rate of reaction increase with increasing
temperature?
● As temp increases, kinetic energy of the
molecules increases
● This means more molecules have energy greater than the activation energy and can therefore react.
● Also as kinetic energy of molecules increases, their
velocities increase resulting in more frequent and
successful collisions.
How would you investigate how rate of reaction varies with temperature?
Na2S2O3(aq) + 2HCl(aq) → 2NaCl(aq) + SO2(g) + S(s)
● This reaction produces a cloudy sulfur precipitate.
● To measure rate, time how long it takes for a cross
underneath the beaker to disappear, using a stopwatch (as more sulfur is produced, it will prevent you from seeing the cross).
● Repeat this at 5+ different temperatures and compare
times taken.
What are some issues with this method?
● The disappeared cross is judged by eye and can
therefore be unreliable.
● There may be a delayed reaction time with the
stopwatch.
● At low temperatures the reaction may be too slow.
● There may not be enough precipitate for the cross to disappear.
How could you analyse the data?
● For a graph of the amount of sulfur against time, it would be a straight line at the beginning as the reaction has only just begun.
● Therefore the gradient of this straight section = rate of
reaction.
● Compare the rate of reaction for each temperature.
● For further analysis, you could even plot a graph of rate of reaction against temperature.
What is a control variable?
A variable that is kept constant throughout the experiment.
In an experiment investigating the effect of
temperature on rate of reaction, what variables will
you control?
● Concentrations of reactants and products.
● Volumes of reactants and products.
● Use the same beaker and cross underneath.
● Use the same person to decide when the cross has disappeared.
How can we keep a substance at a constant
temperature?
Using a water bath keeps the temperature constant. For this experiment you can set up water baths of different temperatures to see how it affects the rate of reaction.
