Information for possible unknown weak acids.
Acid pKa Molar Mass (g/mol)
Sodium hydrogen sulfate 1.99 120.1
Fluoroacetic acid 2.60 78.04
Chloroacetic acid 2.87 94.49
Mandelic acid 3.41 152.1
Acetylsalicylic acid 3.48 180.2
Lactic acid 3.86 90.08
Ascorbic acid 4.17 176.1
Benzoic acid 4.20 122.1
cis-Crotonic acid 4.41 86.09
Succinamic acid 4.54 117.1
Potassium hydrogen phthalate 5.40 204.2
Disodium hydrogen citrate 6.39 263.1
Sodium hydrogen sulfite 7.20 104.1
A student did the potentiometric titration (with a phenolphthalein indicator present). She saw a color change at 8.25 mL of added 0.1000 NaOH. She had started with 0.1000 g of her unknown acid. Five of her volume/ pH measurements are given below:
vol NaOH added (mL) observed pH
2.00 3.71
4.12 4.20
8.25 10.18
10.00 11.71
12.11 12.02
(a) What is the apparent pKa of her acid?
A. 3.71
B. 4.20
C. 10.18
D. 11.71
E. 12.02

the law of conservation of mass states that in a chemical reaction, the total mass of reactants is equal to the total mass of products. because atoms are only rearranged in a chemical reaction, there must be the same number of sodium atoms and chlorine atoms in both the reactants and products

the correct answer is b. a strong acid completely dissociates to its ions when dissolved in water. completely dissociates to and ions. a is incorrect because does not fully ionize to and ions and some remain as the compound . c and d are incorrect because, and do not fall into the category of bronsted lowry acids. a bronsted lowry acid is a proton donor and since both molecules do not have a proton to donate they are not bronsted lowry acids. likewise,   if we use the lewis acid definition, they cannot be acids. a lewis acid is an electron pair acceptor. both and have a complete octet so can not accept any electrons which disqualifies them as acids.