Question

Enter the following data into the calculator and graph pH versus mL of NaOH added.

At the endpoint you should see a rapid change in pH. Identify the two volumes on each side of the endpoint, and determine the color change of the indicator for the end point.

Data Analysis Table

Volume of NaOH Solution Added	pH	Color
0.00 mL	2.79		Clear
1.00 mL	3.99		Magenta then clear
2.00 mL	4.49		Magenta then clear
3.00 mL	4.99		Magenta then clear
4.00 mL	5.34		Magenta then clear
5.00 mL	11.54		Magenta
6.00 mL	12.33		Magenta
7.00 mL	12.63		Magenta
8.00 mL	12.82		Magenta
9.00 mL	12.87		Magenta
10.00 mL	12.97		Magenta
11.00 mL	13.06		Magenta
12.00 mL	13.11		Magenta
13.00 mL	13.16		Magenta
14.00 mL	13.17		Magenta
15.00 mL	13.22		Magenta
16.00 mL	13.25		Magenta
17.00 mL	13.26		Magenta
18.00 mL	13.31		Magenta
19.00 mL	13.32		Magenta
20.00 mL	13.37		Magenta

Answer 1

Here the pH vs volume of NaOH added has been plotted. As one can see the rapid pH change occurs between volume 4 mL and 5 mL of NaOH. So the two volumes at two sides of the endpoint are 4mL and 5 mL. From the table we can see that the colour change between these two volumes is magenta to clear to permanent magenta. So the colour change for the indicator is clear to magenta.