36.8 Summary of methods to monitor the rate of reaction
A. Summary
On-going monitoring method :
1. Change in gas volume with gas syringe (SO2, very soluble in water, small increase in vol of gas collected)
2. Change in gas pressure with pressure sensor (XSO2, very soluble in water, change in pressure is not obvious)
Change in no. of mole of gas in reaction mixture will cause a change in pressure of the system.
3. Change in mass with electronic balance
(X H2, very low density, electronic balance may not be sensitive enough to detect this small change in mass )
Cotton wool plug to allow the escape of the gas produced, at the same time prevent acid from splashing out.
4. Change in colour intensity with colorimeter
(x Colour change)
Absorbance : Due to decrease in [ion], colour of solution fades, less light is absorbed , lower in absorbance.
Quence the reaction (Cause disturbance to the reaction mixture)
5. Change in conc of ( ) with titrimetric analysis [Chemical change]
(Basic Steps: Withdraw, quench, titrate)
2 reactions involved: 1. Reaction // 2. Titration
B. Which method to be used?
Check for the following
Gas : Vol (except SO2) / Pressure (except SO2 )/ Mass (except H2)
One coloured substance: Colour intensity
One Acid / Alkali : Titrimetric analysis
