rp5 rates of reaction Flashcards
what are the 3 ways of measuring the rate of reaction?
- observe how quickly a precipitate forms
- measure the change in mass
- measure the volume of gas given off
how do u calc 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 solution
- measure how long it takes for the cross disappear
how can you measure rate of reaction if the coloured reactants from 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 measure the rate of reaction when there is a change in mass?
- 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 a regular measurements of the volume of gas in the gas syringe
- rate = total volume of gas produced / time
how can you find the rate of reaction after 30 seconds?
plot the results on a graph
- X axis: time
- Y axis: amount of product formed or reactant used
- draw a tangent at 30 secs and calculate the gradient (change in y / change in x) to calc the rate of reaction
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 secs
- repeat with a different concentration of HCL
- compare the rates of each concentration
how could you investigate how sodium thiosulfate concentration affects the rate of reaction when reacted with HCL?
precipitation 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 3x for mean time
- repeat the experiment with different concentrations of sodium thiosulfate
- compare the times for each experiment
