Universal Indicator

Question 1 What are universal indicators?

Question 2 For what purpose a universal indicator is used?

Question 3 Water is neutral. What colour will you get when you add few drops of universal indicator to a a test tube containing water?

Question 4 A solution X and Y is tested with universal indicator. X turns orange whereas Y turns red.Which solution is a stronger acid?

Universal Indicator

The common indicator cannot tell us the relative strength (strong or weak) of an acid or a base.

To  measure the strength of an acid or a base solution we use universal indicators.

Universal indicator is a mixture of many indicators which gives diferent colours at different pH values of entire scale.

It shows different colours at different concentration of  ions in the solution.

pH	colour
0	Dark Red
1	Red
2	Red
3	Orange Red
4	Orange
5	Orange yellow
6	Greenish yellow
7	Green
8	Greenish blue
9	Blue
10	Navy blue
11	Purple
12	Dark purple
13	Violet
14	Violet

 

A drop of the solution to be tested is put on a strip of universal indicator paper.It then undergoes a colour change.The colour produced us then matched with a colour on pH colour chart.We then read the pH value corresponding to this colour from pH colour chart.After knowing pH value we can tell whether the given solution is a weak or strong acid or base.