Question

What color do you expect to observe for the cresol purple indicator (Table 11-3) at the following pH values?

$\left(\mathrm{a}\right)1.0;\left(\mathrm{b}\right)2.0;\left(\mathrm{c}\right)3.0.$

Short answer

The color observed for the cresol purple indicator at pH value 1 has to be identified.

1. $\mathrm{pH}1.0$is prior to the transition range and the color is going to be red.

2. $\mathrm{pH}2.0$is in in the transition range and the color is going to be orange.

3. $\mathrm{pH}3.0$is after the transition range and the color is going to be yellow.

Step-by-step solution

Define Equivalence point

The equivalence point ensures the titration reaction becomes completed and at this point, the number of moles of titrant and the number of moles of analyte remains equal. We cannot see the completion of the titration reaction - the titrant and the analyte becoming equal in stoichiometric proportion, hence we use a chemical compound called indicator called which indicates the end of the reaction by color change. The endpoint refers to the color change and indicates the equivalence point has been reached.

Observe the Table

As we can see in Table 11-3 cresol purple has its transition between$\mathrm{pH}1.2$and$2.8.$In that range, it has an orange color. Before$\mathrm{pH}1.2$it has a red color and after pH$2.8$it has a yellow color.