chapter 7

Question 1

what is the Arrhenius definition of acid and bases?

Answer 1

• acids dissociate in a manner that increases the concentration of protons in solution
• the dissociation of a base increases the concentration of hydroxyide ions

Question 2

what is the Bronsted-Lowry definition of acids and bases?

Answer 2

• an acid is a proton donor
• a base is a proton acceptor

Question 3

what is the Lewis definition of acids and bases?

Answer 3

• acids are electron acceptors
• bases are electron donors

Question 4

what is a compound called when it can act as both an acid or a base?

Answer 4

• amphoteric
  
  • can accept or donate a proton (BL) “amphiprotic”

Question 5

how to name acids with an oxygen:

Answer 5

• prefix hydro, the root of the parent anion, and the suffic -ic acid
  
  • ex. Hydrochloric acid

Question 6

how to name oxyacids?

Answer 6

• for oxyanions that contain the suffix -ate, the acid uses the suffix -ic
• if an oxyanion contains one more O atom than the corresponding “ate” ion, then the acid uses the prefix -per and the suffix “ic acid”
• if an oxyanion contains one fewer O atoms than the corresponding “ate” ion, then the acid uses the suffix -ous acid
• if an oxyanion contains 2 fewer oxygen atoms then the corresponding “-ate” ion, then the acid uses the prefix =hypo and suffix -ous acid
  
  • ClO^- hypochlorite
  • ClO₂^- chlorite
  • ClO₃^- chlorate
  • ClO₄^- perchlorate

Question 7

what is K_w?

Answer 7

• the constant for the autoionization of water
  
  • the reaction of water molecules with each other to form ion s
    
    • K_w = [H₃O⁺][OH^-]
    • the value of K_w at room temperature is 1.0 x 10^-14 and is temperature dependent
    • pH of 7
    • ionizes to a greater extent in warmer temperatures and less in colder temperatures
    • as long as hydronium and hydroxide concentrations are equal, the solution is neutral

Question 8

each acid and base have their own dissociation constants respectively:

Answer 8

• k_a
• k_b

Question 9

what does a high K_a and low k_a signify?

Answer 9

• a high K_a corresponds to an acid that dissociates more readily
• a low k_a corresponds to an acid that does not dissociate to a large degree

Question 10

strong acids vs weak acids:

Answer 10

• strong acids have large k_a values with positive exponents
• weak acids have small k_a values with negative exponents

Question 11

list of strong acids (7):

Answer 11

• hydrochloric acid (HCl)
• hydrobromic acid (HBr)
• hydroiodic acid (HI)
• chloric acid (ClO₃)
• perchloric acid (HClO₃)
• sulfuric acid (H₂SO₄)
• nitric acid (HNO₃)

Question 12

list of strong bases:

Answer 12

• lithium hydroxide (LiOH)
• sodium hydroxide (NaOH)
• potassium hydroxide (KOH)
• cesium hydroxide (CsOH)
• calcium hydroxide (CaOH₂)
• Strontium hydroxide (SrOH₂)
• barium hydroxide (BaOH₂)
• the conjugate base of ammonia (NH₂^-)
• the hydride anion (H^-)
• methoxide (CH₃O^-)
• ethoxide (CH₃CH₂O^-)
• tert-butoxide ((CH₃)₃CO^-)

Question 13

the K_b of a strong base will be?

Answer 13

• very large

Question 14

what are the equations to get pH from an acid or a base?

Answer 14

• pH = -log[H⁺]
• pOH = -log[OH^-]

Question 15

pK_w = pH + pOH is also:

Answer 15

14 = pH + pOH

Question 16

pK_a and pK_b are negative logarithms of?

Answer 16

• k_a and k_b
  
  • _​pH = -log k_a
  • pOH = -log k_b

Question 17

the stronger an acid…

Answer 17

• the weaker its conjugate base

Question 18

A buffer must contain either?

Answer 18

• a weak acid and its conjugate base or a weak base and its conjugate acid

Question 19

the pH of a buffer solution can be calculated using the Henderon-Hasselbach equation:

Answer 19

• pH = pKa + log [A^-]/[HA]
  
  • when equal concentrations of acid and conjugate base are present, the “log” term drops out and pH = pKa
  • choose a buffer where the acid has a pKa close to the desired pH of the buffered solution

Question 20

what is a titration?

Answer 20

• a titration is a technique that aims to determine the concentration of a solution of unknown molarity
  
  • to accomplish this, a solution of known concentration is added until an endpoint is reached (associated with colour change) and the amount of known solution (titrant) required to reach the endpoint can be used to determine the concentration of the unknown reactant (analyte)

Question 21

when does the endpoint of an acid-base titration occur?

Answer 21

• AKA the equivalence point occurs when the original acid or base has been fully neutralized by the added base or acid

Question 22

for polyprotic acids, a complete titartion involves?

Answer 22

• neutraliztion of multiple protons
  
  • polyprotic acids have amphiprotic conjugate bases

Question 23

how to calculate normality:

Answer 23

• normality (N) = moles of equivalents / litres of solution
  
  • equivalents means acidic protins or hydroxide ions

Question 24

the amount of base or acid required to fully neutralize an acid or base is:

Answer 24

• N_acidV_acid = N_baseV_base
  
  • relates the normalities and volumes of the 2 solutions

Question 25

what are indicators?

Answer 25

* indicators are weak acids or weak bases that take on different colors depending on their protonation state * ex. phenolpthalein is colorless when protonated and pink when deprotonated * the pKa of the indicator should be as close as possible to the predicted pH of the solution at its equivalence point

Question 26

what occurs at the half-equivalence points on titration curves?

Answer 26

* where one-half of the titrant required to reach the equivalence point has been added is also the position where one half of our original acid molecules are deprotonated so they exist in half their original form and half in their conjugate base form * at half-equivalence points, pH = pKa

Question 27

equivalence point vs half-equivalence point:

Answer 27

* equivalence point: * represents full neutralization * moles acid = moles base added * solution has virtually no buffering ability * located in the middle of a steep part of the titration curve * half-equivalence point * represents half-neutralization * moles acid - moles conjugate base * solution acts as a relatively effective buffer * located in the middle of a plateau on the titration curve

Question 28

* all strong acid/strong base titrations have an equivalence point at?

Answer 28

* pH 7

Question 29

the equivalence point for a weak acid/strong base titration is:

Answer 29

* always higher than 7 under standard conditions

Question 30

strong acids/weak base titrations have equivalence points?

Answer 30

* below pH 7 under standard conditions

Question 31

the first proton lost in a polyportic acid most readily corresponds to?

Answer 31

* the largest k_a value * the second is harder to lose * the third one is even harder than the last and has the smallest k_a value, so on

Question 32

polyprotic acid titration curves:

Answer 32

Question 33

polyprotic titrations of amino acids:

Answer 33

* nonpolar amino acids have only 2 equivalence points * acidic and basic amino acids have 3 equivalence points