Rate experiments + rate determining step Flashcards
how do you find the initial rate of reaction from a graph?
Draw a tangent at zero
and calculate the gradient
intitial rates method:
- Repeat an experiment several times using different initial concentrations of the reactants ( just change one of the concentrations of the reactants at a time)
- Observe how initial concentrations affect initial rates, and you can find the “order” for each reactant.
iodine clock reaction (initial rate method)
- small amount of sodium thiosulfate and starch added to the reaction mixture, sodium thiosulfate instantly reacts with the iodine that’s being formed
- However once all the sodium thiosulfate has been used up, any more iodine that is formed stays in the solution.
- turning the starch indicator blue-black.
during iodine clock reaction how do you get different times for colour change?
- vary the concentration of iodine or hydrogen peroxide whilst keeping everything else constant.
what is the continuous monitoring method
Recording the amount of product/reactant at regular time intervals.
the step with the slowest rate is known as the…..
Rate determining step
what does order of reaction show regarding the rate determining step
how many molecules of reactant that are involved with the rate determining step
what does the rate determing step help to work out
Reaction mechanisms
- 1st mechanism: with C-Br bond it is a strong bond which is hard to break- so as this is a slow rate of reaction ( rate determing step)
- 2nd mechanism: If OH- concentration is high , positive ions are more likely to collide with the OH- ions- fast rate. OH- ions are not in the rate equation, so can not be involved in the rate determing step