Focus on why each step improves control or observation: cooling limits effervescence, stirring mixes immiscible reactants and white backgrounds make colour loss clearer.
Ethyl butanoate reacts with water.
A student investigated the kinetics of this reaction.
Procedure
Step 150 cm^3 of ethyl butanoate was heated under reflux with a very large excess of water.
Step 2 After 30 minutes a sample of known volume was removed from the reaction mixture and placed in a conical flask.
Step 3 This sample was titrated using aqueous sodium hydroxide solution.
Step 4 Further samples were removed from the refluxing mixture at 30-minute intervals. Each sample was titrated until the titres of three consecutive samples were the same.
The student suggested placing ice in the conical flask before carrying out each titration.
Explain whether or not this suggestion would improve the validity of the data collected.
An answer that makes reference to the following points:
- this suggestion will quench the reaction / slow down the reaction (as reaction mixture at 100^ C )
Either
- it makes no difference (to validity) because the reaction is already very slow / takes 4 hours / no catalyst is used or it will make a difference/improve (validity) because otherwise the reaction will continue producing butanoic acid (at a significant rate)
(1)
Allow stop the reaction Ignore just reference to cooling
Do not award if slowing of reaction is related to other reaction/ slow the titration reaction(s)