Acids and Bases

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Acids and Bases Chapter 10

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Acids and Bases. Chapter 10. Acid-Base Theories. Properties of Acids and Bases Arrhenius Acid-Base Theory Br Ønsted -Lowry Acid-Base Theory strong and weak acids and bases acid nomenclature review. Properties of Acids and Bases. Acids taste sour conduct electricity in aqueous solution - PowerPoint PPT Presentation

Transcript of Acids and Bases

Page 1: Acids  and  Bases

Acids and Bases

Chapter 10

Page 2: Acids  and  Bases

Acid-Base Theories• Properties of Acids and Bases

• Arrhenius Acid-Base Theory

• BrØnsted-Lowry Acid-Base Theory

• strong and weak acids and bases• acid nomenclature review

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Examples of Acids

• citric acid• ascorbic acid• lactic acid• carbonic acid• muriatic acid (aka:

hydrochloric acid)

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writes this equation as:

HCl(g) H+(aq) + Cl−(aq)NB. The H+ ion does not exist as such in aq

solution.The hydronium ion is a hydrated proton, H+.

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some fine print . . .

Some texts, like ours, abbreviate the hydronium ion, H3O+, as H+, called a hydrogen ion.

This is inaccurate! H+ is a bare proton—which cannot exist in

water. Take a look . . .

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the aqueous hydronium ion:

What is the geometry of the hydronium ion?pyramidal

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Bases dissociate in water to produce one or more hydroxide, OH–(aq), ions.

eg. This is a dissociation reaction.

Na(OH)(s) Na+(aq) + OH–(aq)

Ba(OH)2(s) Ba2+(aq) + 2OH–(aq)

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Limitations of the Arrhenius Theory

• restricted to acids & bases in aq solution• doesn’t explain behaviour of all acids or

bases• doesn’t explain certain types of

neutralization reactionsNH3(g) + HCl(g)

NH4Cl(s)

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BrØnsted-Lowry Acid-Base TheoryAcid: proton (H+) donorBase: proton (H+) acceptor

not restricted to aq. solutions

ExplainsNH3(g) + HCl(g) NH4Cl(s)(note that N in NH3 has a lone pair of e-s)

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In order to qualify as a B-L acid, a compound must contain _____________.

(hydrogen)

In order to qualify as a B-L base, acompound must contain ______________ .

(lone pair of e–s— or a negative charge)

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Some B-L Acids & Bases

HCl(g) + H2O(l) H3O+(aq) + Cl−(aq)B-L acid B-L base

NH3(aq) + H2O(l) NH4+(aq) + OH−(aq)

B-L base B-L acid

Water can act as either a B-L acid or base; water is amphiprotic.

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Conjugate Acid-Base Pairs

HCl(g) + H2O(l) H3O+(aq) + Cl−(aq)B-L acid B-L base conj acid conj base

NH3(aq) + H2O(l) NH4+(aq) + OH−(aq)

B-L base B-L acid conj acid conj base

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How are conjugate acid-base pairs related?

By the transfer of a proton.(Look again at previous slide.)

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Identify conjugate acid-base pairs:

HCN(aq) + H2O(l) H3O+(aq) + CN−(aq)acid base c acid c base

H2PO4−(aq) + OH−(aq) HPO4

2−(aq) + H2O(l)acid base c base c acid

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Strong Acids & Bases

A strong acid ionizes 100% in aq soln.eg.HCl(aq) + H2O(l) H3O+(aq) + Cl−(aq)

HClO4(aq) + H2O(l) H3O+(aq) + ClO4−(aq)

100% rxn indicated by the “”

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The “Big Seven” Strong AcidsHCl(aq) hydrochloric acidHBr(aq) hydrobromic acidHI(aq) hydriodic acidHClO4(aq) perchloric acidHClO3(aq) chloric acidHNO3(aq) nitric acid1 mol/L of these ↑ acids = 1 mol/L H3O+(aq)H2SO4(aq) sulfuric acida diprotic acid1 mol/L acid>1 mol/L H3O+

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Review of Acid Nomenclature on the next three slides—taken from nomenclature powerpoint

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Ending of anion name of aciddetermines name of acid

1. anion ends in “-ide”hydro_____ic acid

[hydrobromic acid, HBr(aq), Br-, bromide]2. anion ends in “-ate”

_______ic acid[phosphoric acid, H3PO4(aq), PO4

3-, phosphate]3. anion ends in “ite”

_______ous acid[nitrous acid, HNO2(aq), NO2

-, nitrite ]

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Examples of acidsformula nameHClO2(aq) _______________

chlorous acid_______________ acetic (ethanoic)

acidHC2H3O2(aq)

H3PO3(aq) _______________phosphorous

acid_______________ carbonic acidH2CO3(aq)

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Strong Bases

Strong Bases dissociate 100% in aq soln.

Include the soluble ionic hydroxides of alkali metals alkali earth metals

LiOH Sr(OH)2

NaOH Ba(OH)2

KOH Ca(OH)2 low solubility Mg(OH)2

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These ionic hydroxides dissociate in water 100%:

NaOH(s) Na+(aq) + OH−(aq)

Ba(OH)2 Ba2+(aq) + 2OH−(aq)

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Concentrated vs Dilute Acids/Bases

Concentrated acids/bases:lots of mol/L

eg H2SO4 5 mol/L

Dilute acids/bases:few mol/L, say 0.1

mol/L

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Describe each of the following acids as strong/weak and

dilute/conc1. 0.10 mol/L HNO3(aq)a dilute, strong acid2. 5% (m/v) CH3COOH(aq)a dilute, weak acid3. 10 mol/L H2SO4(aq)a concentrated, strong acid

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Weak Acids and Bases

Ionize less that 100%—usually much less—in aq solution. (eg acetic acid, CH3COOH)

+ H2O H3O+(aq) + CH3CO2

(aq)

represents < 100% yield (an equilibrium)

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Example of weak base, ammonia:

NH3(aq) + H2O(l) NH4+(aq) + OH−(aq)

• ammonia ionizes only a few % • what does this say about the yield of this

rxn?(only a few %)Now indicate conj. acid-base pairs above.

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NH3(aq) + H2O(l) NH4+(aq) + OH−(aq)

wk base acid c. acid c. base

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Homework

10.1 LC # 1 – 12RQ # 1 - 16