Chem%20162-2011%20Lecture%2013

Chem%20162-2011%20Lecture%2013 - CHEMISTRY 162-2011 LECTURE...

Info iconThis preview shows pages 1–5. Sign up to view the full content.

View Full Document Right Arrow Icon
Chem 162-2011 Lecture 13 1 CHEMISTRY 162-2011 LECTURE 13 ANNOUNCEMENTS E-MAIL ATTENDANCE Sign in EXAMS QUIZ
Background image of page 1

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

View Full DocumentRight Arrow Icon
Chem 162-2011 Lecture 13 2 PLAN FOR TODAY : CHAPTER 15 ACIDS AND BASES EQUILIBRIUM Complete buffers and indicators from Tuesday Acid-Base Titrations Major new concepts - Diluted molarity - Half-way point Lewis acids and Bases
Background image of page 2
Chem 162-2011 Lecture 13 3 SIX STRONG ACIDS ET: Discuss strong acids and strong bases and the strengths of their conjugate bases and acids; practice both. V e r y w e a k b a s e (i.e., not a base; K a Acid s p e c t a t o r i o n ) * * ~10 9 HI + H 2 O H 3 O + + I - K cb = ~10 -23 ~10 8 HBr + H 2 O H 3 O + + Br - K cb = ~10 -22 ~10 6 HCl + H 2 O H 3 O + + Cl - K cb = ~10 -20 H 2 SO 4 + H 2 O H 3 O + + HSO 4 - K cb = ~0 HNO 3 + H 2 O H 3 O + + NO 3 - K cb = ~0 HClO 4 + H 2 O H 3 O + + ClO 4 - K cb = ~0 ( H C l O 3 + H 2 O H 3 O + + ClO 3 - )* K cb = ~0 *Strong, but not common, acid. Generally not considered as a strong acid. **These conjugate bases are known as “nominal bases”, i.e., a base by definition, but effectively not a base. All other acids are weak acids, e.g., HAc (acetic acid), H 2 SO 3 , RNH 3 + , BF 3 K a = 1.8x10 -5 HAc + H 2 O H 3 O + + Ac - K cb =5.6x10 -10 K a = 6.2x10 -10 HCN + H 2 O H 3 O + + CN - K cb =1.6x10 -5 Note that the stronger the acid, the weaker the CB; the weaker the acid, the stronger the CB. Arrhenius acid: Anything that provides a proton, e.g., HA, H 2 SO 3 , RNH 3 + LB Acid: Anything tending to give up a proton, e.g., HA, H 2 SO 3 , RNH 3 + Lewis Acid: Anything that accepts an electron pair, e.g., BF 3 STRONG BASES (Most Group 1A and 2A hydroxides [not HOH]) e . g . V e r y w e a k a c i d ( i . e . , n o t a n a c i d ; B a s e s p e c t a t o r i o n ) L i O H O H - + Li + N a O H O H - + Na + Mg(OH) 2 2 O H - + Mg 2+ Ba(OH) 2 2 O H - + Ba 2+ All other bases are weak bases, e.g., RNH 2 , CO 3 2- Arrhenius Base: Anything that provides an OH- group, e.g., NaOH LB Base: Anything that tends to react with a proton, e.g., NaOH, RNH 2 , CO 3 2- Lewis Base: Anything that donates an electron pair, e.g., OH - , RNH 2
Background image of page 3

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

View Full DocumentRight Arrow Icon
Chem 162-2011 Lecture 13 4 ET: First discuss equations, then reverse equations invert K, then Ka x Kb = 10 -14 Write the equil. equations and identify K’s for the following reactions: Weak acid + water (e.g., acetic acid + H 2 O) : HA + H 2 O H 3 O + + A - 1 A s s u m e K a = ~1 x 10 -5 Conjugate base + water (e.g., sodium acetate + H 2 O) : A - + H 2 O HA + OH - 3 K cb = K w /K a = (1 x 10 -14 )/(1 x 10 -5 ) = 1 x 10 -9 Conjugate base + H 3 O + (e.g., sodium acetate + H 3 O + ) :±A - + H 3 O + HA + H 2 O 2 K = 1 / K a = 1/(1 x 10 -5 ) = 1 x 10 5 (or bring to completion; then solve either using HH or reverse + K a ) Weak acid + strong base (e.g., acetic acid + sodium hydroxide) : HA + OH - H 2 O + A - 4 K = 1 / ( K w /K a ) = K a /K w = (1 x 10 -5 )/(1 x 10 -14 ) = 1 x 10 9 (or bring to completion; then solve either using HH or reverse + K a ) Weak base + water (e.g., NH 3 + H 2 O) : RNH 2 + H 2 O RNH 3 + + OH - A s s u m e K b = ~1 x 10 -5 Conjugate acid + water (e.g., sodium acetate + H 2 O) : RNH 3 + + H 2 O RNH 2 + H 3 O + K ca = K w /K b = (1 x 10 -14 )/(1 x 10 -5 ) = (1 x 10 -9 ) Conjugate acid + OH - (e.g., ammonium chloride + OH - ) : RNH 3 + + OH - RNH 2 + H 2 O K = 1 / K b = 1/(1 x 10 -5 ) = 1 x 10 5 (or bring to completion; then solve either using HH or reverse + K b ) Weak base + strong acid (e.g., NH 3 + H 3 O + ) : RNH 2 + H 3 O + RNH 3 + + H 2 O K = 1 / ( K w /K b ) = K b /K w = (1 x 10 -5 )/(1 x 10 -14
Background image of page 4
Image of page 5
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 22

Chem%20162-2011%20Lecture%2013 - CHEMISTRY 162-2011 LECTURE...

This preview shows document pages 1 - 5. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online