3. A student performed an experiment similar to the one that you will perform bu

Question

3. A student performed an experiment similar to the one that you will perform but used different solutions The student's data are presented in the table below Student data for estimating the pH of solutions indicator color 0.1M ThymolMethylBromothymo solutionBlu NaNO red yellow NaNO2 green yellowb HNO3 red HNO2 orangered Blue yellow yellow Red yellow (1) Is a 0.1M NaNO2 solution acidic or basic? What experimental evidence supports your answer? (2) List the acidic solution(s) studied by the student What experimental evidence supports your nswer?

Explanation / Answer

3 For 0.1 M NaNO2

(1) thymol blue turning green: If it changes green then the pH is between 8.2 and 9.1.

methyl red turning yellow indicates: solution of pH more than 6.2

bromothymol blue: changes color over a pH range from 6.0 (yellow) to 7.6 (blue).

Answer: Hence 0.1 M NaNO2 is basic

(2) NaNO3 is acidic because thymol blue changes to red in pH range 1.2-2.8

HNO3 is acidic

thymol blue : 1.2 (red) - 2.8 (yellow)

HNO2 is acidic

Methyl red is a pH indicator; it is red in pH under 4.4, yellow in pH over 6.2, and orange in between, with a pKa of 5.1.

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