Mcat Chemistry Lecture 6

Front 1

____ - has more protons than hydroxide ions

Back 1

Acidic solution

Front 2

____ - has more hydroxide ions than protons

Back 2

Basic solution

Front 3

____ - equal number of hydroxide ions and protons

Back 3

Neutral solution

Front 4

To avoid confusion acids that are solely electron pair acceptors are almost always called ____.

Back 4

Lewis acids

Front 5

____: substances that dissolved in water increase the concentration of h+ ions ( and bases conversely increase concentration of OH- ions)

Back 5

Arrhenius definition

Front 6

____ - an acid is a molecule or ion that donates a proton, a base is a molecule or ion that accepts a proton

Back 6

Bronsted-Lowry
acids donate protons, bases accept protons

Front 7

____ - an acid is an electron pair acceptor, a base is an electron pair donator

Back 7

Lewis
acids accept electrons, bases donate electrons

Front 8

____ - H3O+ , is only a hydrated proton and all protons in water are hydrated

Back 8

Hydronium ion

Front 9

H+ is simply shorthand for the ____

Back 9

Hydronium ion

Front 10

Another char of ____ is slippery when wet.

Back 10

bases

Front 11

____ tastes sour like citric juice, and ____ taste bitter like soap

Back 11

acid
base

Front 12

Acid strength is based on PH scale where P is the ____, so PH is the ____ of the H ion concentration and POH is the ____ the OH ion concentration and PKA is the ____ of the KA

Back 12

negative log function
negative log
negative log
negative log

Front 13

A PH of 7 is ____ at 25 degrees C, and ____ means the concentration of H ions equals OH- ions.
Less than 7 indicates an ____ and greater than 7 indicates a ____.

Back 13

neutral
neutral
acid
base

Front 14

So.. As the h ion concentration goes up the PH goes down due to the ____

Back 14

negative log function

Front 15

Log trends - recognize graph of one
Any log of 1 is 0
Log of a number greater than 1 is ____
Log of a number less than 1 is ____, but no logs of ____ numbers
Log AB = ____

Back 15

0
positive
negative
negative
Log A x Log B

Front 16

Example h ion concentration is 3.16 x 10-4 ____
9.3 x 10-11 indicates ____

Back 16

Ok first look at the exponent so the ph is around 4, then the multiplier indicates that is between 3 and 4 so approximately 3.5
A ph of less than 11 but greater than 10

Front 17

Conjugate Acid is the base plus a ____, the conjugate Base is the acid minus its ____.

Back 17

proton
proton

Front 18

HA + H2O = A- + H3O+
____ --- ____
A- is the ____
H3O+ is the ____
Or you can look at the reverse, HA is the ____

Back 18

Reactants
Products
conjugate base of A (missing a proton)
conjugate acid of water - (has an extra proton)
conjugate acid of A- etc…

Front 19

Water has both a conjugate acid and a base - means it is ____.

Back 19

amphoteric

Front 20

3 characteristics that makes a molecule or ion a strong acid or base

Back 20

BBS
Bond polarity
Bond strength
Stability of the conjugate base

Front 21

(chars) ____ make strong acids

Back 21

High bond polarity, weak bonds and stable conjugate bases

Front 22

____ is an acid with more than 1 acidic proton, in almost all of these acids the second and third protons do not affect the pH, the one important exception is with ____

Back 22

Polyprotic acid
sulfuric acid, H2SO4

Front 23

____
The second proton here is a fairly strong acid in concentrated solutions, it is not strong enough to disassociate significantly but !, in dilute solutions it will affect the pH
And almost none of the ____ comes off until all of the first proton comes off.

Back 23

sulfuric acid, H2SO4
second proton

Front 24

A larger kA indicates a ____ but a smaller pKa indicates a ____.

Back 24

stronger acid
stronger acid

Front 25

____ = acid dissociation constant

Back 25

Ka

Front 26

Ka times Kb = ____
____ = pKw (or 14)

Back 26

Kw
pKa + pKb

Front 27

____ of water (water reacting with itself) to form the ions H+ and OH-
This is ____ because water is very stable and the ions are very reactive, so the equilibrium constant is very small. 10-14 at 25 degrees Celsius
Equilibrium is Kw = H+ X OH-

Back 27

Auto-ionization
endothermic

Front 28

Kw equals 10-14 at 25 degrees Celsius which then means pKw equals ___

Back 28

14

Front 29

Auto-ionization of water
Then drag our log equation out - log (h x oh) = - log H + - log OH
So pKw equals ____ which equals 14

Back 29

pH + pOH

Front 30

A strong acid or base completely ____ in water, so the H ion concentration equals the ____ of the acid

Back 30

dissociates
concentration

Front 31

So a HCl concentration of 2 X 10-3 the ph is ____
Or NaOH is 5 x 10-2 pOH is ____ so ph is ____

Back 31

a little less than 3
between 1 and 2
14 -(1 to 2) so 12 to 13

Front 32

Common strong bases:

Back 32

NaOH
KOH
CaOH2

Front 33

7 common strong acids:

Back 33

HCl
HBr
HI
HClO4
HClO3
HNO3
H2SO4

Front 34

Titrations of pH ____, there is an equivalence point and half equivalence point for each ____
So virtually all of the most acidic proton is removed before any of the second acidic proton is removed

Back 34

polyprotic
consecutive acidic proton

Front 35

Indicator or pH meter to know when we have arrived at the equivalence point
Indicator changes color at the ____ from pKa -1 to pKa +1,
Ph meter is ____

Back 35

endpoint/range
constant meter

Front 36

____
1 molar solution of H2CO3 (carbonic acid)
kA is 4.3 X 10-7 , placed in water very little dissociates
For every molecule that does dissociate we get one h+ and one HCO3-
X = square root of the product of kA and the acid concentration (can ignore acid concentration since it is so small)

43 X 10-8 the square root of it is 6. something times 10-4 , since X is the H ion concentration the pH is between 3 and 4.

For weak base use kB instead of kA, solve for pOH and convert to pH by subtracting pOH from 14.

Back 36

Ph of a weak acid

Front 37

____ - drip a strong acid or base solution into an unknown solution.

Back 37

Titration

Front 38

____ - the strong acid or base solution.

Back 38

Titrant

Front 39

We ____ to find out how many moles are in the solution or the kA of the solution.
We plot it out and get a ____

Back 39

titrate
sigmoidal titration curve

Front 40

The center of the vertical region is the ____, this is where the number of moles in the titrant equal the number of moles of acid or base in the ____.

Back 40

equivalence point or stoichiometric point
original solution

Front 41

____, where the number of moles of acid or base from the titrant equal half the number of moles of the original acid or base

Back 41

Half equivalence point!!

Front 42

At the ____ all the original HA has changed to A-

Back 42

equivalence point

Front 43

When the titration curve is horizontal the pH does not change much when we add either acid or base - a ____

Back 43

buffered solution

Front 44

Buffered equation - henderson hasselbach equation - ____

Back 44

pkA = pH - log A/HA

Front 45

At the ____ we have equal numbers of HA and A- (half has been changed)
Back to the henderson hasselbach now we throw stuff in and!!, ____ at the half equivalence point,

Back 45

half equivalence point
pkA = pH

Front 46

Center of the first horizontal region of a titration curve ____.

Back 46

pH = pkA