Acids, Bases And Buffers Flashcards Preview

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Flashcards in Acids, Bases And Buffers Deck (36):
1

What is true in dynamic equilibrium?

- most chemical reactions are reversible
- reactants combine to give products
- product can fall apart to give reactants

2

What happens when a system is in a state of dynamic equilibrium?

- will adjust to establish equilibrium conditions
—-> go forward or backwards (toward products or reactants) until equilibrium is restored

3

What is an example of an equilibrium equation?

Hemoglobin with O2
He + 4O2 Hgb (O2)4
- will move towards bound or unbound depending on dynamic equilibrium of system

4

What is the equilibrium constant (K)?

When there is a balance between reactants and products the system in a State of equilibrium
- equilibrium constant (K) is the numerical description of that balance

5

The state of equilibrium is defined by what group of laws?

Thermodynamics

6

What is the meaning of K?

- as k increases, the reaction increasing favors the products.
- as k decreases, the reaction increasing favors the reactants.(the reverse reaction becomes more favorable)

7

What to Ka, KB, Ksp, and Keq stand for?

Ka= K for weak acids
Kb= K for weak bases
Ksp= solubility
Keq = generic equilibrium constant

8

How do solids and liquids affect equilibrium?

- concentration of liquids and solids is nearly constant
- comprise a different phase from where the reaction occurs
—> therefore, the concentration of liquids or solids does NOT appear in the equilibrium constant expression
- but they are part of the equilibrium constant VALUE

9

What happens if you add or remove products?

- ADD products—> equilibrium will shift toward REACTANTS
- REMOVE products—> equilibrium will shift toward PRODUCTS
** will shift toward whatever there is less of in order to maintain balance *

10

How does changing volume affect equilibrium reactions?

* only impacts equilibrium reaction when at least 1 reactant or product is a GAS *
- solids and liquids are not compressible
- decreasing volume favors the smaller number of gas particles (think of squeezing many gas particles into fewer gas particles)

11

How area acids and bases defined in terms of the Bronstead definition?

- ACID= proton (H+) donor—> HCl, H2SO4
- BASE= proton (H+) acceptor —> NaOH-, NH3-

12

What happens when an acid donates a proton?

- it is converted to its conjugate base
HA —> H+ + A-
(Acid). (Conjugate Base)

13

What happens when an a base accepts a proton?

It is converted to its conjugate acid
B + H+—> BH+
(Base). (conjugate acid)

14

What is represented in this equation?
HCl ——> H+ + CL-

HCl (acid) is giving up a proton H+ to form its conjugate base Cl-
- if the reaction ran in reverse, Cl- would accept the H+ to form the conjugate acid HCl
—> these are called conjugate acid-base pairs

15

What is an amphoteric species?

- can behave as either an acid or a base (H2O)
H+ + H2O—-> H3O (H2O as the conjugate base
H2O—-> H+ + OH- ( H20 as the conjugate acid)

16

What are the relative strengths of conjugate acids and bases?

- the stronger the acid, the weaker the conjugate base
- the weaker the acid, the stronger the conjugate base
Strong acid= more determined to give up a proton
Strong base- more likely to accept a proton

17

T/F weak acids ionize 100% in water?

False
Strong acids ionize 100% in water
Weak acids do not, they establish an equilibrium

18

In water, what do weak bases do?

Establish equilibrium by accepting a proton

19

What is pH?

pH=-log[H+]
Based on self ionization of water

20

What is the pH scale?

Quantitively describes “acidity”or “alkalinity” of a solution
PH= 7: defines neutrality point
Ph>7: basic solution
PH<7: acidic solution

21

What is a mathematical operator “p” in chemistry?

An instruction to do something to a set of numbers

22

What does p mean?

P = -log
Take the log of something and change the sign

23

What is a buffer and what can they do?

- a pH buffer is a solution that resists changes in pH
- may contain a weak acid and its conjugate base
HA + OH- —-> H2O + A-
A- + H+—-> HA
* the common ion effect suppresses weak acid/base properties of HA and A-
- simplifies equilibrium calculations

24

What are 4 truths of pH buffers?

1.) the buffer in solution resists changes in pH
2.) contains weak acid and weak base
3.) Henderson-Haselbach equation is used to determine the ratio of weak acid to its conjugate base at a give pH
4.) When concentration of weak acid and its conjugate base are equal,the pH is equal to the pKa

25

What is drug utilization by the body determined by?

The degree of ionization or non-ionization

26

What is try of non-ionized drug?

- is lipid soluble (lipophillic)
- readily penetrates BBB and placental barriers
- hydrophobic/non water soluble

27

Is the ionized dry water soluble?

Yes

28

What does knowing the degree of ion/non-ionization help you determine?

Drug effectiveness

29

What are 3 steps to determine drug effectiveness?

1.) is the drug a weak acid or a weak base?
- weak acid= salt drug (Na, Ca, Mg)
- weak base= drug chloride, drug sulfate
2.) what is the pKa of the drug?
* this is your reference**
PKa= pH where 50% of drug is in ionized form and 50% is in non-ionized form
3.) the pH of the target solution the drug is placed in?
Normal body pH ins 7.4

30

How do weak acids behave as pH falls or rises?


Acid + acid= more non-ionized
Acid + base = more ionized

31

How do weak bases act as pH increases or decreases?

Base + base= more non-ionized
Base + acid= more ionized

32

The greater the non-ionized portion of the drug the ____________ the transfer to ________ and ________.

Greater
Brain
Fetus

33

A substance that accepts H+ is said to be _______________.

Protonated

34

What is true regarding ionized vs non-ionized forms of acids/bases and their conjugates?

- the non-ionized form of a weak acid is the acid, and the ionized form is its conjugate base

- the non-ionized form of a weak base in the base, while the ionized portion is the conjugate acid

35

T/F PKa is different for each weak acid and each weak base.

True

36

How does trapping of LA in fetal circulation occur?

- pH of fetus is lower than maternal circulation
- circulating non-ionized drug crosses placental barrier
- once in fetus (lower pH/acidic), equilibrium is re-established —> greater % ionized, less works and unable to leave—> trapping in fetal circulation