[问答题]
In an investigation i
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rgl h9y8r6po l0ei7y2a number of sealed conical flasks, each containing a solution of water and carbonic acid.
Each conical flask was placed in a water bath maintained at a constant temperature. At regular time intervals, samples of the solution were taken from each conical flask and measured using a pH probe.
The results are shown in the table.
1.1Identify the dependent and independent variables in this investigation.
1.2State one variable that must be kept constant in this investigation to ensure the results are valid.
2Describe the relationship between the temperature, time and pH of the solution.
3Predict the pH of the dilute carbonic acid solution at $40^{\circ}C$ after 60 minutes.1
4.1Calculate the rate of change in pH between 30 - 40 minutes and 40 - 50 minutes for the trial kept at $40^{\circ}C$.
4.2Suggest a reason for the difference in the rate of change you calculated in (i).
5.Suggest one improvement to the design of this experiment and state whether it would increase the accuracy or reliability of the results.
