Question

You are given the following experimental data for an unknown solution. What is the pH range of the unknown? Explain in detail how you determined the pH range.

Indicator	pH Range	Color Change	Experimental Result
Methyl violet	0.1 to 2.7	Yellow to Violet	Violet
Alkali Blue	9.4 to 14.0	Violet to Pink	Violet
Methyle Red	4.4 to 6.2	Red to Yellow	Yellow
Bromothymol Blue	6.3 to 7.6	Blue to Yellow	Yellow

Answer 1

With methyl violet we get violet colour which means we had higher than range of 0.1 to 2.7

Hence pH range of our solution > 2.7

with alkali blue ( 9.4 to 14) ( violet-pink) we got violet which mean our solution has less than 9.4   ( since when pH < 9.4 solution is violet)

pH range of solution less than 9.4

with methyl red ( 4.4 to 6.2) ( red to yellow) we got Yellow which means solution pH range is above 6.2

with bromothymol blue ( 6.3 to 7.6) ( blue to yellow) we got yellow hich means solution pH above 7.6

now comparing 4 results and narorwing pH range it is clear pH range 7.6 to 9.4    satisfies all 4 conditions

hence pH range 7.6 to 9.4