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.

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

 

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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