Acids & Bases & Oxidation-Reduction Reactions Flashcards
What are the two main theories on acids and bases?
- Arrhenius theory of acids & bases
- bronsted-lowry theory
What is the Arrhenius theory of acids and bases?
- acid: substance, when dissolved in water, dissociates to produce hydrogen ions
- hydrogenion: H+ also called “proton”
- but Arrhenius not explain observation of protons do not exist as H+ in aq solutions, rather they interact W/ water to form hydronium ions H3O+
- base: substance, when dissolved in water, dissociates to produce hydroxide ions OH-
What is the bronsted-lowery theory?
- acid: proton (H+) donor
- base: proton (H+) acceptor
What are the acid-base properties of water?
- Water possesses both acid and base properties aka amphiprotic
- water used most commonly used as solvent for both acids & bases
- solute-solvent interactions btwn-water & both acids & bases promote solubility & dissociation
What are conjugate acids and bases?
HX + Y (reversible arrows) X- + HY+
- Conjugate acid: what base becomes after it accepts a proton
- > HY+ is conjugate acid of baseY
- Conjugate base: what acid becomes after it donates its proton
- > X- is conjugate base of acid HX
- Conjugate acid -base pair: acid & base on opposite sides of equation
- > HY+ & Y
- > HX & X-
What is acid & base strength based off of?
- based on degree of dissociation (not measure of concentration)
- strong acids & bases: reaction with water is virtually 100% (strong electrolytes)
What are some strong acids and bases? *
Strong acids: HCl, HBr, HI HNO3:nitric acid H2SO4: sulfuric acid HClO3: chloric acid HClO4: perchloric acid Strong bases: NaOH, KOH, Ba(OH)2 All metal hydroxides
What are some weak acids & bases?
-only small % dissociates (weak electrolytes)
Ex: acids: acetic acid & carbonic acid
Ex: bases: ammonia, pyridine, Aniline
What does self-ionization mean?
- dissociation of water
What is the ion product constant for water?
K(w)= [H3O+][OH-]
= 1.0 x 10^-14 (@ 25°C)
What is the pH scale?
Scale that indicates acidity or basicity of a solution
- 0 (very acidic) to 14 (very basic)
- pH= -log[H3O+]
How can pH impact H3O+ and OH- concentrations?
- if add an acid, [H3O+] increases & [OH-] decreases
- if add a base, [OH-] increases & [H3O +] decreases
- if equal amounts of base and acid then equal amounts of [H3O+] & [OH-]
What does [H3O+] & [OH-] equal to?
1.0x10^-14 = [H3O+] [OH-]
How can you calculate pH?
1.0x10^-14 = [H3O+] [OH-] pH= -log [H3O+]
How can you find [H3O+] from pH?
[H3O+]= 10^-pH
What is a neutralization reaction?
Reaction of an act with a base to produce salt and water
What is titration?
Analytical technique to determine concentration os an acid or base
- measures amount of standard solution to neutralize second, unknown solution
What is a burst? Indicator?
Burnt: long glass tube calibrated in mL which contains standard solution
Indicator: substance which changes as pH changes
What is a polyprotic substance?
Donates or accepts more than one proton per formula unit
ex: H2SO4 produces 2H+ ions
What is a buffer solution?
Solution which resists large change in pH when either acids or bases are added
-buffer is lechatelier’s principle
What is the buffer process?
- act to establish an equilibrium btwn conjugate acid/base pair
- consist of either: weak acid & its salt (conjugate base) or weak base & its salt (conjugate acid)
What does the addition of a base(OH-) do to a buffer solution?
- OH- will react with H3O+ producing H2O
- acid in butter system dissociates to replace H3O+ consumed by + base
- net result is to maintain pH close to initial level
- loss of H3O+ (stress) compensated by dissociation of acid to produce more H3O+
What does the addition of an acid ( H3O+) do to a buffer solution?
- H3O+ from acid will increase overall
- conjugate base in buffer system reacts with H3O+ to form more acid
- net result is to maintain H3O+ concentration & pH close to initial level
- compensated by reaction of conjugate by gain of H3O+ (stress) to produce more acid
What is buffer capacity?
Measure of ability of a solution to resist large changes in pH when strong acid/strong base is added
How do you calculate pH of a buffer solution?
[H3O+]=(Ka[acid]) / [conjugate base]
pKa= -log(Ka)
What is the henderson-hasselbalch equation?
pH= pKa + log (B/A)
Used to find pH of a buffer solution
What are the parts of an oxidation -reduction process?
- Oxidation: defined by one of following:
- loss of e-, loss of hydrogen atoms, gain of oxygen atoms
- Reduction: defined by one of following:
- gain of e-, gain of hydrogen, loss of oxygen
- cannot have oxidation without reduction*
What does an an oxidizing agent do? Reducing agent?
Oxidizing Agent:
- is reduced, gains electrons, causes oxidization
Reducing Agent:
- is oxidized, loses electrons, causes reduction
What is a voltaic cell?
Electrochemical cell that converts stored energy into electrical energy
- separates 2 half reactions
- makes electrons how through a wire to allow oxidation and reduce to occur
- salt bridge completes circuit
Where does oxidation and reduction occur?
- Oxidation - anode
- reduction-cathode
What is electrolysis?
Uses electrical energy to cause nonspontaneous oxidation-reduction reactions to occur (reverse of a voltaic cell)
