equilibrium
rate of forward reaction equals rate of backwards reaction
equilibrium constant
ratio of product concentrations : reactant concentrations
How does changing the initial reactant concentrations affect K
K is a ratio and therefore remains the same as long as the temperature remains constant
How does changing the temperature affect K
increasing temp. increases the rate of reaction, increasing K
decreasing temp. decreases the rate of reaction, decreasing K
What is the mainchemical reaction of experiment O
Fe ^3+ + SCN ^1- = FeSCN ^2+
What colour is FeSCN ^2+
orange - red
what are the parts of the equation
A = εbc
A = absorbance
ε = proportionality constant/molar absorptivity
b = path length of light through sample
c = concentration of sample in M
What wavelength is the absorbance measured at and why
447nm
it is deep blue which is opposite to the orange-red colour of FeSCN ^2+
In Lab O, is Fe ^3+ or SCN- in excess and why
Fe ^3+ is in excess so that the reaction can go to completion. All SCN- is used up
Why do all solutions of FeSCN ^2+ include a high concentration of H+
does not interfere with reaction but prevents Fe ^3+ from reacting with water to form compounds
Experiment O Process Timeline (8)
- 4 erlenmeyer flasks are prepared.
- Constant volume and higher M of Fe ^3+
- Varied vols of SCN- and H2O but constant total volume - flasks are stirred to reach equilibrium
- spectrometer used on blank cuvette at 447nm
- flask 1 temp is measured, then scanned by spectrometer in a cuvette at 447nm
- steps 1-4 repeated for each flask
- 4 new flasks are prepared
- constant volume and lower M of Fe ^3+
- varied vols of SCN- and H2O (adds up to 10) - spectrometer absorbance test repeated for 4 new flasks
