Spectroscopy TM Flashcards
What can spectroscopy be used for?
It can be used to determine the concentration of a solution by measuring how much light it absorbs
How does spectroscopy work?
White light is shone through a filter which is chosen only to let the colour of the light throught that is absorbed in the sample. The light then passes through the sample to a colorimeter and it shows how much light was absorbed by the sample
What is the relationship between the concentration of a coloured solution and the light it will absorb?
The more concentrated a solution = the more light it will absorb
How do you find the unknown concentration of a sample?
Produce a calibration graph (curve)
What are the axis on a calibration graph?
X-axis –> concentration of ion
Y-axis –> relative absorbance
Describe the method to how you would find the unknown conc of a sample:
Measure absorbencies of known concs of solutions
Plot results on graph
Measure absorbence of sample
Read concentration off of graph
Why would the colour be more intense when using a colorimeter? (in terms of concentrations of the solution)
If a solution is more concentrated it means more ions are present in a given volume and more will interact so the colour will be more intense.
What is the instrument called that is used to investigate the colour of solutions?
spectrophotometer
Why is spectroscopy a useful method for measuring the concentration of coloured ions?
Because it is easy to get loads of readings and you can work out the concentration quite quickly.
You can measure very low concentrations
Doesn’t use up any of the substance
Doesn’t interfere with any reactions
What does ∆E stand for
in ∆E = hν = hc/λ?
Energy absorbed (J)
What does h stand for
in ∆E = hν = hc/λ?
Plack’s constant (Js)
What does ν stand for
in ∆E = hν = hc/λ?
Frequency of light absorbed (Hz)
What does c stand for
in ∆E = hν = hc/λ?
The speed of light (m s-1)
What does λ stand for
in ∆E = hν = hc/λ?
Wavelength of light absorbed (m)
What is Planck’s constant? Give units
6.63 x 10(-34) Js
