Question

Titration of a Weak Acid: Data Sheet
Unknown acid: C (letter or number on the unknown bottle)
Mass of the Unknown acid: 0.2016g		Concentration of NaOH(aq): 0.10M
	Volume NaOH added	pH
	0.5	4.26
	1.0	4.42
	1.5	4.58
	2.0	4.71
	2.5	4.82
	3.0	4.92
	3.5	5.02
	4.0	5.11
	4.5	5.27
	5.0	5.41
	5.5	5.48
	6.0	5.50
	6.5	5.59
	7.0	5.73
	7.5	5.80
	8.0	5.93
	8.5	6.06
	9.0	6.26
	10	6.53
	10.5	7.06
	11	9.65
	11.5	10.98
	12	11.23
	12.5	11.39
	13	11.53
	13.5	11.51
	14	11.58
	14.5	11.65
	15	11.72
	15.5	11.76
	16	11.81
	16.5	11.84
	17	11.87
	17.5	11.89	Calculate Ka for your unknown acid. If your unknown is polyprotic, calculate Ka at both the equivalence points. (Show work) possible answers: Potassium hydrogen phthalate (Monoprotic) [C8H5KO4 ] Molar Mass: 204.2212 4.82 pKa= 5.4 Ascorbic acid (Monoprotic) [C6H8O6 ] Molar Mass: 176.1241 pKa= 4.3 Maleic acid (Diprotic) [C4H4O4 ] Molar Mass: 116.0722 pKa 1= 1.83, pKa2= 6.07 Calculate the initial concentration of your acid. Recall that the original volume of the solution was 0.100 L [Acid]initial = Using your calculated value of Ka and the initial concentration of the acid, calculate the initial pH of your acid. Set up an ICE table. You may need to use the quadratic formula. NaOH(aq) + C8H4O4(aq) ---> NaC8H4O4(aq) + H2O(l)