{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

chapter 18 - Chapter 18 Acid-Base Equilibria I II III IV V...

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

View Full Document Right Arrow Icon
Chapter 18 Acid-Base Equilibria I. Acids & Bases in Water II. Autoionization of Water and pH III. Brønsted-Lowry Acids and Bases IV. Weak Acid Equilibria V. Weak Bases VI. Trends in Acid Strength VII. Acidic & Basic Salt Solutions VIII. Generalizing the Brønsted-Lowry Concept IX. Lewis Acids & Bases I. Acids & Bases Arrhenius Acid-Base Theory : (oldest & simplest) Arrhenius acid = a substance that has H in its formula & yields H + ions when dissolved in water Arrhenius base = a substance that has OH in its formula & yields OH - ions when dissolved in water Ex : HCl( aq ) + NH 3 ( aq ) → Cl - ( aq ) + NH 4 + ( aq ) acid base (donor) (acceptor) Q : How can a proton be an H + ion? Ans : hydrogen atom (H) 1 proton + 1 electron hydrogen ion (H + ) 1 proton Brønsted-Lowry acid = proton (H + ) donor Brønsted-Lowry base = proton (H + ) acceptor
Background image of page 1

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

View Full Document Right Arrow Icon
Conjugate base = a species with one fewer H + than its conjugate acid Ex : OH - is the conjugate base of H 2 O. Conjugate acid = a species with one more H + than its conjugate base Ex : H 3 O + is the conjugate acid of H 2 O. Conjugate acid-base pair = two species whose formulas differ by a single H + Ex : HCN / CN - H 2 O / H 3 O + H 2 O / OH - Conjugate Acid-Base Pairs Exercise : What is the conjugate acid of each of the following: (a) HS - (b) CH 3 CH 2 NH 2 (c) SO 4 2 - Solution : Exercise : What is the conjugate base of each of the following: (a) HS - (b) C 6 H 5 COOH (c) H 2 SO 4 Solution : Exercise : Identify the Brønsted acids and bases on the left and their conjugates on the right: ) O( H ) ( PO H ) ( HPO ) ( O H 2 - 4 2 2- 4 3 l aq aq aq +  → + + a) ) O( H (aq) CO (aq) OH (aq) HCO 2 2- 3 - - 3 l +  → + b) c) ) ( HCO ) ( SO ) ( CO ) ( HSO - 3 - 2 4 - 2 3 - 4 l aq aq aq +  → +
Background image of page 2
Strong acids are strong electrolytes: ) ( NO ) ( O H 100% ) ( O H ) ( HNO 3 3 2 3 aq aq l aq + + + Weak acids are weak electrolytes: ) ( F ) ( O H ) O( H ) HF( - 3 % 1 ~ 2 aq aq l aq + + + Relative Acid-Base Strength Some substances have negligible acidity in water: reaction no ~ ) O( H ) OH( CH 2 3 → + l aq The stronger an acid, the weaker its conjugate base. The weaker an acid, the stronger its conjugate base. The stronger a base, the weaker its conjugate acid. The weaker a base, the stronger its conjugate acid. Common Strong Acids: HCl HClO 3 HNO 3 HBr HClO 4 H 2 SO 4 HI Common Strong Bases = hydroxides of Group 1A metals: LiOH, NaOH, KOH,… Heavy Group 2A metals: Ca(OH) 2 , Ba(OH) 2 , Sr(OH) 2 most common Strong Acids & Strong Bases Memorize all of these! Exercise: Identify the stronger base of each pair: a) Br - or CN - b) ClO - or Cl - c) OH - or NO 3 - d) F - or CH 3 - f) H 3 O + or H 2 O
Background image of page 3

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

View Full Document Right Arrow Icon
Figure 18.2 The extent of dissociation for weak acids. Weak acid: HA( aq ) + H 2 O( l ) H 2 O + ( aq ) + A - ( aq ) Weak acids dissociate very slightly into ions in water. Strong acids dissociate completely into ions in water. HA( g or l ) + H 2 O( l ) H 3 O + ( aq ) + A - ( aq ) HA( aq ) + H 2 O( l ) H 3 O + ( aq ) + A - ( aq ) K c >> 1 K c << 1 K c = [H 3 O + ][A - ] [H 2 O][HA] K c [H 2 O] = K a = [H 3 O + ][A - ] [HA] stronger acid higher [H 3 O + ] larger K a smaller K a lower [H 3 O + ] weaker acid Acid-Dissociation Constant, K a II.
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.

{[ snackBarMessage ]}