A Student was handed three solutions,labeled 1,2, and 3. she was told that one s

Question

A Student was handed three solutions,labeled 1,2, and 3. she was told that one solution contained 0.1M HNO3, another contained 0.1M KOH, and the third contained a solution of thymol blue. when she mixed equal amount of two of the solutions she got the following results: 1 mixed with 2 gave a blue solution. 1 Mixed with 3 gave a colorless solution. 2 mixed with 3 gave a red solution. identify the solution.

solution 1 was _______ solution 2 was ______ solution 3 was _____

she then mixed equal amounts of all three solutions. what color did she get?

explain

Explanation / Answer

Thymol blue is used as pH indicator and it exhibits different colors at different pH. When pH is below 1.2, the color of thymol blue is red, from pH= 2.8 to 8.0, color of thymol blue is yellow and when pH is above 9.6, thymol blue exhibits blue color.

Out of three given solutions, HNO3 and KOH solutions are colorless and mixing equal amount of them will result in neutral colorless solution. This is the observation upon mixing solution no. 1 and 3. Therefore, it can be concluded that remaining solution no. 2 is thymol blue solution.

When solution no. 2 (thymol blue) is mixed with solution no. 1, blue color is obtained. Hence, solution no. 1 must be basic i.e. 0.1M KOH.

When solution no. 2 (thymol blue) is mixed with solution no. 3, red color is obtained. Hence, solution no. 3 must be acidic i.e. 0.1M HNO3

Therefore, solution 1 is 0.1M KOH; solution 2 is thymol blue and solution 3 is 0.1M HNO3

When equal amounts of three solutions are mixed, pH of the resulting solution will be neutral (as equal moles of HNO3 and KOH will neutralize each other). In neutral pH, thymol blue exhibits yellow color. Therefore, color of the resultant solution will be yellow.

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