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CHAPTER 8: ACID – BASE EQUILIBRIUM 4 U CHEMISTRY

P 526 – SEE KEY IDEAS
-examples f acids and bases.

8.1: The Nature of Acid – Base Equilibria:
-Arrhenius acids – H ions in water, bases – hydroxide ions in water -acids – sour, turn blue litmus to red (pink), conduct electricity -bases – bitter, soapy taste, slippery, conduct electricity, turn red litmus to blue

Bronsted – Lowry Theory:
-acids – donate proton, bases accept proton
-ex: HCl donates proton to water ( not reversible )
-ex: water donates proton to ammonia – reversible
-Amphoteric substances: ____________________________________________________________ -Advantage of B-L definition:
-1. reactions can be identified as acid-base neutralization reactions without water -2. salts that form acidic or basic solutions when dissolved can be explained

Reversible Acid – Base Reactions
-many B-L acid-base reactions are reversible
-Conjugate acid – base pair – differ only by one H
-ex: H2O and H3O +
A Competition for Protons
-stronger c-acid succeeds in donating the most protons, has a weaker c-base -stronger c-base succeeds in accepting the most protons, has a weaker c-acid -the strong acid and strong base are always on the same side of the reaction arrow -99 % ionized = strong acid, ex: HCl

SUMMARY p 531
p 532 practice # 1, 2, 3.

The Autoionization of Water
-2 molecules may collide and one molecule accepts a proton from the other – see p 532 -equilibrium of the reversible reaction – can write the constant -Kw = [H +] [OH –1 ] = (1.0 x 10 –7 )2 = 1.0 x 10 –14 -Kw changes at different temp ( remember concept from ch 7 ) -so pH of pure water changes with diff temp

-but pure water always neutral since # protons = # hydroxide ions

Strong Acids
-ionize more than 99 % in water ex: HCl
-monoprotic acids – have only one ionizable H ex: HNO3
p 537 practice # 4, 5, 6.

Strong Bases:
-ionic substances, dissociate 100 % in water, but not all are very soluble -ex: NaOH and other gp 1 hydroxides (soluble), Mg(OH)2 and other gp 2 hydroxides (slightly soluble) -DON’T drink NaOH ! it will react with the tissues of your mouth ant throat and destroy them!! -but people regularly eat Mg(OH)2 - as an antacid – it doesn’t dissolve on the way to the stomach, and then only dissolves enough to react with stomach acid to neutralize it -[OH –1]= concentration of strong base x # OH –1 groups per formula unit. Ignore OH –1 from water p 540 practice # 8, 9, 10, 11.

Hydrogen Ion Concentration: pH = – log [H +]
-used to express conc that are smaller than 1 because neg exponents can sometimes be confusing -SIG DIG’s count ONLY for the decimal numbers of a pH value -pOH = – log[OH –1]
-pKw = – log Kw = 14 at SATP
-pOH + pH = 14 at SATP

Measuring pH
-indicators – weak acids or weak bases that change colour with the addition or removal of the ionizable hydrogen ex: bromthymol blue ( BTT ) that we used in an investigation -pH meters – change of electrical conductivity is converted into pH

pH of Strong Acids and Bases:
-conc of hydrogen ion = conc of the strong acid if the acid is monoprotic, H+ from water is negligible -OMIT calculations of acids that are diprotic or higher.
-[OH –1] = concentration of strong base x # OH –1 groups per formula unit. Ignore OH –1 from water

SUMMARY p 549
p 546 practice # 12, 13, 14, 15ab, 16a.
p 549 practice # 17, 18, 19.
p 549 – 550 section 8.1 practice # 1, 2, 3, 4.

8.2: Weak Acids and Weak Bases
ex: _________________________________________________________________________________ -form equilibrium solutions between ionized and molecular forms

Weak Acids: _________________________________________________________________________

-ex: ________________________________________________________________________________

Weak Bases:
-react with water to ionize the water so OH –1 ions exist in the solution -weak bases are proton...
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