Unit 10- Acids and Bases

• Acidity• Alkalinity• Arrhenius acid• Arrhenius base• Bronsted-Lowry acid• Bronsted-Lowry base• Buffer • Electrolyte

• Hydrogen ion• Hydronium ion• Indicator• Neutralization• pH scale• Salt• Titration

Properties of Acids

• Have sour taste– ***take my word, don’t

taste lab chemicals

• Can conduct electric current in solution– Electrolytes– Good conductor= strong

acid– Poor conductor= weak acid

• Turns blue litmus paper red “blue to red a-cid”

• Most common acids are liquid or gas

• React with metals to produce H2 gas– Above H2 in Table J will

react (single-replacement)

• React with bases to form salt and water– Neutralization (double-

replacement

• Can generate hydronium ions H3O+ in water

• pH less than 7

Acids

• Sulfuric- car batteries• Ascorbic- tomatoes

Properties of Bases

• Have bitter taste– ***take my word, don’t

taste lab chemicals

• Can conduct electric current in solution– Electrolytes– Good conductor= strong

base– Poor conductor= weak

base

• Most common bases are solid

• React with acids to form salt and water– Neutralization (double-

replacement

• Can generate hydroxide ions OH- in water

• Turns red litmus paper blue “blue base”

• pH greater than 7

Bases

• Sodium bicarbonate

Acid and Base Strength

• Due to degree of ionization• Complete dissociation-strong acid or base

Definitions of Acids and Bases

• Arrhenius Theory- – Arrhenius acid- produces H+ or H3O+ as the only

positive ions in solution• Hydrogen ions will attract to water molecule and form

hydronium ions

– Arrhenius base- produces OH- ions in solution• Except!!! Not all bases have OH- ions

• Drawbacks: – Limited to aqueous solutions– Can’t classify amphoteric substances (substances

that act as bases and acids)

Arrhenius acid is a substance that produces H+ (H3O+) in water

Arrhenius base is a substance that produces OH- in water

Definitions of Acids and Bases con’t• BrØnsted-LowryTheory-

– B-L acid- proton donor– B-L base- proton acceptor– Proton = hydrogen ion that has lost its electron

A Brønsted-Lowry acid is a proton donorA Brønsted-Lowry base is a proton acceptor

acidconjugate

basebaseconjugate

acid

Definitions of Acids and Bases con’t

• All Arrhenius acids are also B-L acids• B-L bases expand the substances that can be

considered bases

Naming acids

• If an acid molecule forms 1 H ion it’s a:– Monoprotic acid (HCl)

• If an acid molecule forms 2 H ions it’s a:– Diprotic acid (H2SO4)

• If an acid molecule forms 3 H ions it’s a:– Triprotic acid (H3PO4)

Naming acids con’t

• For binary acids:– Hydro + element name – ine + ic + acid– Ex: HCl- hydrochloric acid– Try HF- _________________________

• For ternary acids: containing H, O and another element– 3rd element name, modify to end in –ic or –ous +

acid– Ex: HNO3- nitric acid nitrogen –ogen + ic + acid

– Try HNO2- _____________________

Naming bases• Name of positive ion + hydroxide

– Ex: Ba(OH)2- barium hydroxide– Try KOH- ____________________

Anion Ending Acid Name

-ide hydro-(stem)-ic acid

-ate (stem)-ic acid

-ite (stem)-ous acid

No oxygen

More oxygen

Less oxygen

Reactions with acids and bases

• Acids and metals- – Use Table J in Ref Tables– Acid will react with anything above H2

– Single replacement rx’s Zn(s) + 2HCl(aq) H2(g) + ZnCl2(aq)

• Neutralization reactions-– Arrhenius acid + Arrhenius base salt + water– Equivalence pt- pt at which neutralization is

complete; when H30+ ion = OH- ions

Neutralization Rx• Words:Hydrochloric acid + sodium hydroxide water + sodium chloride

• Chemical formulas: HCl(aq) + NaOH(aq) H2O(l) + NaCl(aq)• Ions:H+(aq) + Cl-(aq) + Na+(aq) + OH-(aq) H2O(l) + Na+(aq) + Cl-(aq)

• Omitting spectator ions: H+(aq) + OH-(aq) H2O(l) or

H3O+(aq)+ OH-(aq) 2H2O(l)

Neutralization Rx’s con’t

• Diprotic acid + dihydroxy base makes 2 water molecules– Ex: Ca(OH)2 + H2SO4 2H2O + CaSO4

• Acids and bases with unequal H+ and OH- needs to be balanced– Ex: ___Mg(OH)2 + __HCl __H2O + ___MgCl2

(two) (one)

• Salts produced- ionic substance with a metal and nonmetal or polyatomic ion

Titrations• Process of adding a measured volume of an

acid or base of known concentration to an acid or base of unknown concentration until neutralization occurs

• Cacid x Vacid = Cbase x Vbase (known) (known) = (unknown) (known) molarity x volume = molarity x volume

• Standard solution= soln of known concentration• There needs to be a 1:1 ratio of H+ to OH-

– Diprotic ex: 2.5M H2SO4 = 5M H+

– Triprotic ex: 2MH3PO4 = 6M H+

– Dihydroxy base ex: .5MBa(OH)2 = 1M OH-

Acidity and Alkalinity of Solutions

• Relative strength of an acid or base in terms of their H+ or OH- concentrations

• H2O H+ + OH-– Le Chateliers principle [H+] = [OH-]– If one increases the other decreases

• If you add HCl to water H+ increases so it becomes more acidic

pH scale

• Expresses the strength of acids and bases

• Instead of using very small numbers, we just use the NEGATIVE power of 10 on the Molarity of the H+ (or OH-) ion.

• pH change of 1 is a 10 fold increase or decrease in ions

pH indicators

• Substance that changes its color when it gains or loses a proton (H+ ion)

• Universal indicators are a mix of a few indicators

• pH meter- electric instrument with probes sensitive to H3O+ creates voltage between probes

Buffers

• Solutions that resist change in pH

• Weak acid or base• Usually a weak acid and

its conjugate base• Stabilizes pH

– Foods, shampoo, antacids, blood