Observe Color for Cresol Purple Indicator at PH 1.0 2.0 & 3.0 Ques

1. Consider malonic acid, CH2(CO2H)2. It’s a diprotic acid, which we can abbreviate H2M. Calculate the pH and concentrations of H2M, HM- , and M-2 in 0.100 M Na2M.

2. Find the pH and concentration of each species of arginine in a solution of 0.0100 M arginine·HCl. (Hint: arginine itself is triprotic. But, arginine in arginine·HCl is in the form H2A + )

3. How many mL of 0.500 M NaOH should be added to 100 mL of solution containing 5.00 g of phosphoric acid to get a pH of 8.50?

4. The diprotic acid H2A has a pKa = 6.00 and pK2 = 10.00. (a) At what pH is [H2A] = [HA- ]? (b) At what pH is [HA- ] = [A2- ]? (c) Determine the principal species at the following pH values: 2.00, 8.00, and 12.00.

5. Consider the titration of 50.0 mL of 0.100 M HClO4 with 0.050 M KOH. Find the pH at the following volumes of base added, and make a graph of pH versus Vb: Vb = 0, 10, 25, 90, 99, 100, 101, and 110 mL. (You can – and should – use Excel to calculate and/or plot!) *** You must UPLOAD the Excel file to Moodle ***

6. A volume of 50.0 mL of the dibasic compound B (0.050 0 M, pKb1 = 5.00, pKb2 = 9.00) was titrated with 0.500 M HCl. Find the pH at the following volumes of acid added and make a graph of pH versus Va: Va = 0, 1, 2.5, 4, 4.8, 5, 5.2, 6, 7.5, 9, 9.8, 10, 10.2, 11 and 12 mL. (You can – and should – use Excel to calculate and/or plot!) *** You UPLOAD the Excel file to Moodle ***

7. a) What color do you expect to observe for cresol purple indicator at pH 1.0, 2.0 and 3.0? b) What color would you expect cresol red (two transitions!) to be at pH 0, 1.0, 6.0, and 9.0?

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