RP5 Rates of Reaction Flashcards
what are three ways of measuring the rate of a reaction?
- observe how quickly a precipitate forms
- measure the change in mass
- measure the volume of gas given off
how do you calculate the rate of reaction?
rate of reaction = amount of product formed or reactant used / time
how could the rate of reaction be measured if a precipitate is produced?
- place piece of paper with a black cross below the reaction vessel and observe this cross through the solution
- measure how long it takes for the cross disappear
how can you measure rate of reaction if the coloured reactants form a colourless solution?
time how long it takes for the reactants to turn colourless
why is the precipitate and colour change rate experiment not very reliable?
it is very subjective - people might disagree over the exact point when the mark disappears or the solution changes colour
how can you find the rate of reaction of a reaction after 30 seconds?
plot results on a graph
- x axis: time
- y axis: amount of product formed or reactant used
draw a tangent at 30 seconds and calculate the gradient (change in y / change in x) to calculate the rate of reaction
how can you measure the rate of reaction when there is a change in mass?
carry out the experiment on a mass balance:
- measure initial mass
- combine reactants
- take measurements of the mass at regular intervals as the reactants react
- rate = change in mass / time
how can you measure the rate of reaction when a gas is given off?
- add reactants to a conical flask
- immediately attach a gas syringe to the conical flask with a bung to ensure minimal gas escapes
- take regular measurements of the volume of gas in the gas syringe
- rate = total volume of gas produced / time
how could you investigate how sodium thiosulfate concentration affects the rate of reaction when reacted with HCl?
precipitate produced so measure the time it takes to cover a cross
- add 30cm^3 of sodium thiosulfate to a conical flask
- add 10cm^3 dilute HCl
- measure the time it takes for the cross to disappear
- repeat three times for mean time
- repeat the experiment with different concentrations of sodium thiosulfate
- compare the times for each experiment
what are the units of rate of reaction if you are measuring a change in mass?
g/s
what are the units of rate of reaction if you are measuring the volume of gas given off?
cm^3/s
how could you investigate how HCl concentration affects the rate of reaction when magnesium is added?
gas is produced so the volume of gas produced can be measured:
- place the HCl in a conical flask
- add the magnesium ribbon and quickly fit the bung and gas syringe
- record volume of gas collected every 10 seconds
- repeat with a different concentration of HCl
- compare the rates for each concentration
