Question

CHEM 104 Homework 6 2. (15 points): Chapter 18.1, 4.4-5 A chemist is testing the properties of a newly-discovered pair of acids, A1 and A2. She determines them both to be monoprotic and performs several experiments to compare their acid strength: • • Experiment 1: Adding a few drops of bromophenol blue (see Fig. 19.9 in textbook) to 1.0 M aqueous solutions of each acid results in a yellow color for A1 and a green-blue color for A2. Experiment 2: Measuring the conductivity of the same two solutions results in a higher measurement for Al than for A2. Experiment 3: Addition of a Zn strip to each solution resulted in vigorous bubbling in the case of Al and mild bubbling in the case of A2. Based on these experiments, which is the stronger acid? Explain how the results of each experiment support your choice, and also identify the gas inside the bubbles in Experiment 3.

Answer 1

Dear Student

2) Al is stronger acid than A2. Experimenti? Bromophenol blue is an acid-base indicator similar to phenolphthalein. It changes colour from yellow at pH = 3.0 to blue at pH = 4.6. For Al colour is yellow For A2 colour is green-blue pH of Al < pH of A2 Hence Al is more acidic Experiment 2: Since stronger acids dissociates more into ions as compared to weaker acids, so we can say that stronger acids have more no. of ions for conduction of electricity: Al has higher conductivity value. A2 has lower conductivity value Hence, Al is stronger acid than A2. Experiment 3: metals like Zinc react vigorously with stronger acids and form Hydrogen gas. Zn reacts with Al resulting in vigorous bubbling. zn reacts with A2 resulting in mild bubbling. Hence Al is more acidic than A2 from all the above 3 exprestiments we can conclude Al is stronger acid than A2 Gas evolved in experiment 3 is Hz. Znt Acid Salt & H₂ ma V

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