CL 18- rates year 13 Flashcards
rate of reaction
definition
the change in concentration of a reactant or product in a given time
half-life
definition
the time taken for a concentration to halve
rate-determining step
definition
the slowest step in a multi-step reaction
concentration-time graph for zero order
shape of graph
straight line, negative gradient
concentration-time graph for first order
shape of graph
curve with negative gradient
concentration-time graph for second order
shape of graph
steeper curve with negative gradient
how would you use a conc-time graph to calculate the rate?
- draw a tangent
- gradient=conc/time
how would you use a conc-time graph to measure half life?
- half total conc, draw along to find the time at this conc
- repeat by halving the conc again
how can we use half lives to distinguish between first and second order conc-time graphs?
first order reactions have a constant half life
equation for rate constant k, for first order
k = ln2 / t₁₂
rate-concentration graph for zero order
shape of graph
straight horizontal line (constant rate)
rate-concentration graph for first order
shape of graph
straight line with positive gradient
rate-concentration graph for second order
shape of graph
curved with positive gradient
examples of measuring rate by continuous monitoring methods
- monitoring by gas collection
- monitoring by mass loss
- monitoring with colorimeter
(iodine clock reaction)
initial rates method
- measure amounts of solutions using a burette/syringe (sodium thiosulfate, sulfuric acid, starch)
- differ the volumes of water and potassium iodide added for 5 test tubes, to measure the rate at different concentrations
- start a timer when added water and potassium iodide
- stop timer when colour change to blue/black
- 1/t (rate) plotted against concentration
idk what i was on this is such a bad explanation my bad guys
