Mark two consecutive halvings on the graph with working, compare their time intervals and use repeated halving rather than linear subtraction for later amounts.
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.
A graph of the results obtained by the student is shown.
The student plotted V_final -V_t on the y -axis against time on the x -axis.
V_final is the volume of the titre at 4.5 hours.
V_t is the volume of the titre at time t .
Explain how the data collected indicates first order kinetics.
Show your working on the graph.
The student concluded that the reaction is first order overall.
Explain whether or not this statement is valid.