Which of these indicators is best suited to distinguish between a solution that has a pH less than 5 and one that has a pH greater than 5?
a. phenolphthalein |
b. bromthymol blue |
c. methyl red |
ANSWER:
Indicator function area:
Indicators | Acid color | pH range of color change | Base color |
a. phenolphthalein | colorless | 8.2 - 10.0 | pink |
b. bromthymol blue | yellow | 6.0 - 7.6 | blue |
c. methyl red | red | 4.8 - 6.0 | yellow |
We can see in table that only methyl red indicator works in the range of pH less than 5 and pH greater than 5. So, methyl red indicator is best suited to distinguish between a solution that has a pH less than 5 and one that has a pH greater than 5.
Hence, option C is correct.
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