Acid Base Lecture Kotz

Acid Base Lecture Kotz - Acid-Base Chemistry Weak Acid...

Info icon This preview shows pages 1–4. Sign up to view the full content.

View Full Document Right Arrow Icon
1 Acid-Base Chemistry Strong vs Weak Acids and Bases Based on the extent of ionization in solution Weak Acid Ionization Constant 5 3 2 3 3 2 [ ][ ] 1.8 10 [ ] CH CO H O K CH CO H + = = × Bronsted Acid Proton Donor Bronsted Base Proton Acceptor Polyprotic Acids Capable of donating more than one proton
Image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
2 Amphiprotic means able to act as an acid or a base [i.e. can gain or lose a proton] and amphoteric means able to react with an acid or a base. Ex. Aluminium oxide is amphoteric in acid: Al 2 O 3 + 6HCl 2AlCl 3 + 3H 2 O in base: Al 2 O 3 + 2NaOH + 3H 2 O 2NaAl(OH) 4 NaAl(OH) 4 is sodium aluminate Water is both amphoteric and amphiprotic Exercise 17.1 a) Write a balanced equation for the reaction that occurs when H 3 PO 4 , phosphoric acid, donates a proton to water to form the dihydrogen phosphate ion. Is the dihydrogen phosphate ion an acid, a base, or amphiprotic? b) Write a balanced equation for the reaction that occurs when the cyanide ion, CN - , accepts a proton from water to form HCN. Is CN - a Bronsted acid or base? a) H 3 PO 4(aq) + H 2 O (l) H 2 PO 4 - (aq) + H 3 O + (aq) Since H 3 PO 4 is a weak acid, H 2 PO 4 - can act as both an acid and a base (amphiprotic). It’s preferred direction is going to be dependent upon the K a value of the dihydrogen phosphate ion. b) CN - (aq) + H 2 O (l) HCN (aq) + OH - (aq) The CN- is acting as a Bronsted base because it is a proton acceptor. Conjugate Acid-Base Pairs Differ by one H +
Image of page 2
3 Exercise 17.2 In the following reaction, identify the acid on the left and its conjugate base on the right. Similarly, identify the base on the left and its conjugate acid on the right. HNO 3(aq) + NH 3(aq) NH 4 + (aq) + NO 3 - (aq) Answer HNO 3 and NH 4 + are acids; NH 3 and NO 3 - are bases. The Autoionization of Water Pure water will autoionize to an extent that is temperature dependent Where Does the pH Scale Come From? In any sample of pure water a certain number of water molecules will interact with one another H 2 O (l) + H 2 O (l) H 3 O + (aq) + OH - (aq) This is known as the autoionization of water Hydronium and hydroxide are produced in a 1:1 ratio At 25 o C, the concentration (molarity) of H 3 O + or OH - at any given time (in pure water) is 1.0x10 -7 M The product of the concentrations is given by: [H 3 O + ][OH - ] = [1.0x10 -7 ][1.0x10 -7 ] = 1.0x10 -14 = K w K w = Ion product constant of water The product of the hydronium and hydroxide ion concentration in any solution must always be concentration in any solution must always be K w Implications: As the concentration of H 3 O + goes up, OH - goes down and vice versa such that the product is always K w Concentrations of H 3 O + greater than 1.0x10 -7 will have a pH less than 7 (given pH = -log[H 3 O + ]) and be acidic Concentrations of H 3 O + less than 1.0x10 -7 will have a pH greater than 7 and be basic (alkaline) Exercise 17.3 A solution of the strong acid HCl has [HCl] = 4.0x10 -3 M.
Image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Image of page 4
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern