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.

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