pH, pOH, Buffers, Equilibrium

Question 1

What’s equilibrium

Answer 1

The rates of the forward and reverse reaction are equal, so the concentrations of products and reactants don’t change. We consider the reaction “over” bc they are moving forward & backward at the same pace (constantly).

Question 2

What’s a buffer?

Answer 2

A solution that resists changes in pH even when a strong acid or base is added
It’s made of a weak acid and its conjugate base

Question 3

when do you use -log?

Answer 3

when you know the concentration (or molarity)

Question 4

when do you use 10^-

Answer 4

when you know the pH or pOH

Question 5

why must a buffer by made from a weak acid and its conjugate base?

Answer 5

If it was a strong acid, it would dissociate 100% completely and contribute to the h30+ concentration. Allows the weak acid which doesnt dissociate to be available to react with added base without adding h30+ to the solution in general.

Question 6

why does the pH not change when a strong base or acid is added to the buffer?

Answer 6

strong base reacts with the weak acid
HC2H3O2 + NaOH -> H2O + C2H3O2- + Na+
strong acid reacts with conjugate base
C2H3O2- + HCl -> HC2H3O2 + Cl-

Question 7

pH measures

Answer 7

potential of hydrogen measure h30+ concentration

Question 8

pOH

Answer 8

potential of hydroxide measures OH- concentration

Question 9

Are all chemical reactions reversible?

Answer 9

technically yes

Question 10

what does it mean to be neutral?

Answer 10

equal amounts of h3o+ and OH- concentration

Question 11

What reacts with what when involving a buffer?

Answer 11

strong base reacts with weak acid

weak acid reactions with conjugate base

Question 12

what does it mean to reach equilibrium?

Answer 12

the reactions keeps going (doesnt stop). theres no change in concentration so its called equilibrium

Question 13

what does it mean to reach equilibrium?

Answer 13

the reactions keeps going (doesnt stop). theres no change in concentration so its called equilibrium

Question 14

in the reaction, what does it mean if there is onlyt a forward arrow?

Answer 14

it indicates that the reaction has reached equilibrium

Question 15

why is the pH scale 1-14

Answer 15

because when water dissociation reaches equilibrium, the concentrations equal 10^-14

Question 16

strong acids or bases when calculating pH/pOH

Answer 16

they dissociate 100%, we dont consider the reverse reaction so we just calculate pH and pOH using the acid/base concentration as the H+ or OH- respectively (allowed to plug in molarity because of that)
-no reverse reaction

Question 17

weak acids and bases when calculating pH/ pOH

Answer 17

equilibrium constants (ka and kb) can be used to determine how much an acid or base dissociates into ions by comparing how much product is formed to how much reactant remains. This can let you find pH and pOH of weak acids and bases by giving you a h3o+ and OH- concentration

Question 18

weak acids and bases formula

Answer 18

how much reactant left

this equals how much an acid or base dissociates
(this is all calculated one its reached equilibrium)

Question 19

weak acids and bases formula

Answer 19

how much reactant left

this equals how much an acid or base dissociates
(this is all calculated one its reached equilibrium)

Question 20

Dissociation of strong acids and bases vs weak

Answer 20

strong dissociate 100% so 2 M HCl or NaOH has an H+ or OH- concentration equal to 2M
weak do not dissociate 100% and therefore must be told the H+ or OH- concentration

Question 21

Smaller concentration of H+ equals ________

Answer 21

higher pH (lower values) 
1 is most acidic, 14 is least

Question 22

Smaller concentration of H+ equals ________

Answer 22

higher pH (lower values) 
1 is most acidic, 14 is least

Question 23

affinity of the acetate ion for protons compared to water molecules for protons?

Answer 23

the Acetate doesnt give up its H’s very easily bc it dissociates less than 100% so the weak acid is very good at holding onto its protons compared to water molecules