Flashcards in 18.2 concentration-time graphs Deck (19):
What is continuous monitoring?
Continuous measurements taken during the course of a reaction
What can continuous monitoring be used to plot?
A concentration-time graph
In colorimetry how is the wavelength of light passing through a coloured solution controlled?
Using a filter
In colorimetry, what is measured?
Amount of light absorbed
How can you analyse the reaction of propane and iodine with an acid catalyst?
What is measured by colorimetry in the reaction of propane with iodine with an acid catalyst?
The rate at which iodine is used up i.e. the rate at which the colour fades, this can be confirmed by colorimetry
What is the complimentary colorimetry filter for iodine?
How do you carry out the reaction of propane and iodine with an acid catalyst in order to determine the rate?
- prepare standard solutions of iodine
- select complimentary colour filter
- set zero colorimetry with water
- measure standard absorbance
- plot a calibration curve of absorbance against concentration
- carry out the reaction, take absorbance readings at timed intervals and use the calibration curve to measure concentration
- plot concentration-time graph to determine order
What does a 0 order concentration time graph look like
A straight line with a negative gradient with the gradient = k
What does a 1st order concentration-time graph look like?
Downward curve with a decreasing gradient
What does a 2nd order concentration-time graph look like?
A steeper downward curve that tails off more slowly
What is the half-life?
The time taken for half the reactants to be used up?
In 1st order reactions what is the half-life?
constant (exponential decay)
How do you calculate k for 1st order reactions from rate?
Calculate the gradient of a concentration-time graph to get the rate and sub into the rate equation
What is the gradient of a concentration-time graph?
How do you calculate k for 1st order reactions from half life?
K=in2+ (Time taken for half-life)
How do many drugs break down?
By exponential decay
What are drugs with short half lives used for?