I'm putting extra points on this. I really need help.

18 c

19 b

20 a

21 a

Explanation:

18 LiOH is a powerful base citric acid is a weak acid so when we mix a powerful base with a weak acid mixture become basic

when we mix powerful base with a powerful acid it becomes neutral(need to take equal quantities)

when we mix powerful acid with weak base mixture becomes acidic

when we mix weak acid with weak base we cannot tell what happens to find this we need to do some calculations

19 when the ka value is high it becomes more acidic

20 A polyprotic acid is an acid that can donate more than one proton or hydrogen atom per molecule to an aqueous solution. In contrast, a monoprotic acid (e.g., HCl) can only donate one proton per molecule.

so here it has 3H so it can donate 3H+

in here we need to write the ionization of the acid in water

do the answer is a

21 A proton acceptor is another name for a base, which is the opposite of an acid. In the Broensted-Lowry definition, a base is a negatively charged ion that will react with, or accept, a positively charged hydrogen ion. Since a hydrogen ion is a proton, the base is called a proton acceptor.

an acid is any proton donor, and a base is any proton acceptor. The focus of this definition is on donating and accepting protons, and is not limited to aqueous solution. The Brønsted-Lowry definition of acids and bases is one of two definitions we commonly use