10 - Acids And Bases

Question 1

Arrhenius acids and bases

Answer 1

Defined by dissolution in water to excess of H+ or OH-

Question 2

Bronstead-Lowry acids and bases

Answer 2

Defined by donation or reception of H+

Question 3

Lewis acids and bases

Answer 3

• defined by donation or reception of electron pairs

- acids accept electron pair

Question 4

Amphoteric species

Answer 4

• reacts like acid in basic environment and vice versa

- amphiprotic may behave as BL acid or base: water and polyvalent species

Question 5

Consistency of equilibrium constants

Answer 5

• only temperature dependent

- otherwise 100% constant

Question 6

Log and other mathematical properties

Answer 6

Log1=0
Log10=1
Log100=2
Log1000=3
Logxy=logx+logy
-log(n x 10^-m)=(-logn)-log(10^-m)=m-logn=m-0.n

(because n is between 1 and 10, -logn will be between 0 and 1)

(6x10^-3)^2 = 36x10^-6

Question 7

Water dissociation constant and K of WA and WB

Answer 7

Kw [water disossiation constant] =[H3O+][OH-]=10^-14

• weak acids defined by Ka less than 1
• weak bases defined by Kb less than 1
• conjugate of a strong acid of base is inert

Question 8

Hydrolysis and neutralization reactions

Answer 8

• hydrolysis: salt ions react with water to give back acid and base
• neutralization reactions form salt and sometimes water

Question 9

Titrations

Answer 9

• oft carried out between acids/bases or oxidation/reduction pairs
• titrant (known [] and volumes) added to titrand (known volume, unknown [])
• WAWB titrations rarely performed

Question 10

equivalence points

Answer 10

• for SASB titration, equivalence point will be at 7 but that isn’t always the case: otherwise, leans toward stronger of reactants
• equivalence point may be observed by use of an indicator
• equivalence point generally has steepest point on curve for any titration

Question 11

SASB titrations

Answer 11

Flat- vertical - flat

Question 12

WA (titrand) SB (titrant)

Answer 12

• more gradual initial curve, vertical, flat
• starting point is farther from zero than SASB
• SA (titrant) and WB (titrand) is inverse

Question 13

Polyvalent titration curve

Answer 13

• equivalence points at steep segments

- half equivalence points (corresponding to pka values) between equivalence points at flat segments

Question 14

Buffers

Answer 14

• generally composed of WAWB conjugate pair
• big flat parts of curve
• greatest buffering capacity is about 1pH range within pKa of acid of buffer

Question 15

Henderson-Hasselbalch

Answer 15

• pH=pKa+log[A-][HA]
• greater [], same ratio increase buffering capacity - less of a pH change with addition of A or B
• use normality / equivalence equation to get []: N1V1=N2V2
• optimal buffering occurs when pH = pKa