Lab 6

Question 1

Arrhenius definition

Acid/Base

Answer 1

Acids: substances that increase the concentration of hydrogen ions (H+) when dissolved in water
Bases: substances that increase the concentration of hydroxide ions (OH-) when dissolved in water

Question 2

Lewis definition

Acid/Base

Answer 2

Acids: accept an electron pair from another substance
Bases: donate an electron pair to another substance

Question 3

Bronsted- Lowry acid

Acid/Base

Answer 3

Acids: transfers a proton (H+) to another substance
Bases: accept a proton from another substance
HA (aq) + H2O (l) —> A- (aq) + H3O+ (aq)

Question 4

Conjugate Acid/Base

Answer 4

Acids/Bases that differ by only the presence of a proton
HA (aq) + H2O (l) —> A- (aq) + H3O+ (aq)
Acid HA- conjugate base is A-
Base H2O- conjugate acid is H3O+

Question 5

Strong Acid

Answer 5

Substance completely transfers its protons to water or in other words completely dissociates in water
Weak Conjugate Base

Question 6

Strong Base

Answer 6

Substance completely protonated in water

Weak Conjugate Acid

Question 7

Weak Acid

Answer 7

Donates a portion of its protons to water (partially dissociates)

Question 8

Weak Base

Answer 8

Partially protonated in water

Question 9

Acid- Dissociation Constant (Ka)

Answer 9

Extent of the dissociation of a weak acid can be calculated by using the equilibrium constant for the dissociation of the weak acid in water, called this

Question 10

Base- Dissociation Constant (Kb)

Answer 10

Extent of protonation of a base in water can also be calculated by using the equilibrium constant for the reaction, called this

Question 11

Ion- Product Constant

Answer 11

Kw = Ka*Kb = 1.0e-14 (at 25degree Celsius)

Question 12

Autoionization

Answer 12

pH of neutral solution determination

Ex. Water can donate a proton to another water molecule in a pure solution of water because it’s amphoteric

Question 13

Amphoteric

Answer 13

Water,

Means that it can act as either an acid or base

Question 14

Acid- Base Titration

Answer 14

If concentration of an acid or base is unknown, than its concentration can be found by adding a known concentration of base or acid

Question 15

Analyte

Answer 15

Base of known concentration

Question 16

Titrant

Answer 16

Acid of unknown concentration

Question 17

Equivalence Point

Answer 17

Point at which the solution is neutralized occurs when a stoichiometrically equivalent amount of base has been added to an acid

Question 18

Endpoint

Answer 18

Point of color change on the indicator

Indicator should be chosen for endpoint close to equivalence point of titration

Question 19

Titration Curve

Answer 19

Monitored pH can be graphed as a function of the volume of known base/acid added
On curve, equivalence point occurs when a sharp rise in pH occurs

Question 20

Henderson- Hasselbalch Equation

Answer 20

pH= pKa + log( [A-]/[HA])

Question 21

Purpose

Answer 21

To determine the identity of an unknown acid by determination of the equilibrium constant via titration