Chapter 18 - rates (Year 13) Flashcards
A proposed mechanism for this reaction takes place in several steps
Suggest 2 reasons why it is unlikely that this reaction could take place in ones step
Stoichometry in rate equation does not match the stoichometry in overall equation
Collision with more than two ions is unlikely
State the effect of a higher temperature on the rate constant, k
Rate constant will increase
How would you know on a concentration-time graph it is a first order relationship
Downward slope
Half life is constant
Which apparatus could be used to determine the effect of the concentration of cuso4 (aq) on the rate of reaction
Colorimeter
What is the formula to work out Activation energy
M = -Ea / R
M = gradient
R = 8.314
To ger kJ then /1000
How to work out A from graph
A = e to the power of y intercept
Explain how the student could determine the activation energy, Ea, for the reaction graph of k and T
Plot a graph using ln k ( Y axis) and 1/T (x axis)
Work out the gradient
Then use formula –> m = -Ea / R
to work out Activation energy
The student sample a reaction mixture in a colorimeter and records the absorbance.
Explain why absorbance decreases during the experiment
Iodine is a yellow colour and the concentration of I2 decreases
What is meant by the term rate determining step
The slowest step
A student investigates the rate of reaction by monitoring the concentration of bromine over time
Suggest how the concentration of the bromine could have been monitored
Measure reduction of colour of Bromine
Suggest a different experimental method that would allow the rate of this reaction to be followed over time
Measure volume of gas (CO2)
Why would the use of excess HCOOH ( or any substance) ensure that the order with respect to HCOOH is effectively zero
Concentration of HCOOH would be constant
Suggest apparatus that allows gas volume to be collected
1dm ^ 3 gas syringe
