Titration - teachnlearnchem.com

NaOH = ? M HCl = 0.10 M Initial HCl Final HCl HCl added Initial NaOH Final NaOH NaOH added 3.00 mL 5.35 mL 0.85 mL 0.00 mL 1.10 mL 1.10 mL

1.10 mL 2.10 mL 1.00 mL 0.77 mL 2.10 mL 5.10 mL 3.00 mL 2.30 mL 5.10 mL 10.10 mL 5.00 mL 3.85 mL 10.10 mL 20.10 mL 10.00 mL 7.70 mL

20.10 mL 35.10 mL 15.00 mL 11.5 mL Molarity of NaOH M1.V1 = M2.V2 (0.10 M)(1.10 mL) = (M2)(2.35 mL) Titration Lab Teacher Notes: Step 1) Mix 5 liters of 0.100 M HCl M1V1 = M2 V2 (0.100 M) (5000 mL) = (12.1 M) (x mL) requires 41.3 mL of 12.1 M HCl for 5 L of 0.100 M HCl Step 2) Mix 5 liters of 0.13 M NaOH M = mol L requires 0.65 moles NaOH in 5 L or 26 g NaOH in 5000 mL water Step 3) Prepare indicators (500 mL of each indicator) Phenolphthalein should be mixed fresh each year (for ammonia titration with HCl) Use methyl orange for titration of vinegar (with NaOH) Use bromthymol blue for titration of NaOH with HCl

Day 1) Get used to indicators and using a buret use litmus paper to identify the acid and the base Then check pH of each using pH paper Add ~1 mL of universal indicator into a 150 mL Erlenmeyer flask, Add acid and note color change, then add base and note color change Rinse out Erlenmeyer flask and add 1 mL of phenolphthalein. Add base and record the color of phenolphthalein, finally, add acid Until a faint pink color persists. Repeat several times to reach the endpoint. I use household ammonia (as base) and vinegar (as acid). Day 2) Set up calibration curve with 0.1 M HCl and unknown [NaOH] calculate concentration of ammonia and vinegar. What is the pH of a solution made from mixing 50 mL of 3.0 M HCl with 75 mL of 2.0 M NaOH? HCl H1+ + Cl1M= 3.0 M = NaOH mol L Na1+ + OH1M= x mol 0.050 L

2.0 M = x = 0.15 mol HCl mol L x mol 0.075 L x = 0.15 mol NaOH pH = 7 What is the pH of a solution made from mixing 50 mL of 3.0 M HCl with 80 mL of 2.0 M NaOH? HCl H1+ + Cl1mol L M= 3.0 M = NaOH M= x mol 0.050 L

2.0 M = x = 0.15 mol HCl M= mol L 0.01 mol xM= 0.130 L X = 0.0769 M OH1- Na1+ + OH1mol L x mol 0.080 L x = 0.16 mol NaOH 0.16 mol OH1- 0.15 mol H1+ 0.01 mol OH1- Kw = [H+][OH-] 1x10-14 = [H+][0.0769 M] [H+] = 1.3 x10-13 pH = 12.89 Credit: Baughman et al., Science 297, 787 (2002)