rate equations

Question 1

what is a reaction mechanism

Answer 1

a series of steps that together, make up the overall equation

Question 2

what is a rate determining step

Answer 2

the slowest step in the reaction mechanism of a multi step reaction. it will appear in the rate equation.

Question 3

what is an intermediate

Answer 3

species formed in one step of a multi-step reaction that is used up in a subsequent step and is not seen as either a reactant or a product of the overall reaction.

Question 4

what does each letter in the Arrhenius equation represent

Answer 4

A= pre-exponential frequency factor
e= natural log constant
Ea= activation energy
R= gas constant
T= temperature in kelvin (+273)

Question 5

arrhenius eq with lnk subject

Answer 5

lnk= lnA - (Ea/ RT)

Question 6

arrhenius eq with T subject

Answer 6

Ea/ (R x (lnA - lnK))

Question 7

arrhenius eq with Ea subject

Answer 7

Ea = RT(lnA - lnK)

Question 8

arrhenius eq with A subject

Answer 8

A= K/ e^-(Ea/RT)

Question 9

how can the arrhenius equation be used to draw straight line graphs

Answer 9

lnK=Y
-Ea/R=m
1/T=x
lnA=C

Question 10

describe the iodine clock experiment

Answer 10

-hydrogen peroxide reacts with iodide ions to form iodine
H2O2(aq) + 2H+(aq) + 2I–(aq) → I2(aq) + 2H2O(l)
-add sodium thiosulfate to the reaction mixture
-add starch which acts as an indicator
-the sodium thiosulfate reacts with the iodine
-time how long it takes for a blue-black colour to appear
-repeat experiment varying the concentrations of iodine
and record the time
-this can be used to work out the order of the reaction

Question 11

how to work out the order of a reaction from graphs

Answer 11

• using a concentration/time graph work out the gradient at different points on the graph
• use this to plot a rate/concentration graph
• work out the order