unit 10- acids and bases acidity alkalinity arrhenius acid arrhenius base bronsted-lowry acid...
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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