CA & CB
What’s something you could find in your house that’s an acid?
What’s something you could find in your house that’s a base?
Acid: Lemons, vinegar
Base: Baking soda, soap, bleach
What is the pOH when [OH-] = 6.3 x 10-4 M
pOH = -log (6.3 x 10-4)
pOH = 3.2
What is the pOH when pH = 2.2
pOH = 11.8
What is the purpose of a buffer solution?
To resist changes in pH
Which high school did Mrs. Torres attend?
Redondo Union High School
Consider the reaction
HSO4-(aq) + H2O(l) ⇌ SO42-(aq) + H3O+(aq)
Which chemical acts as the base?
H2O
Because it accepts the H+
What is the pH when there are 0.034 moles of H+ in a liter of solution?
pH = -log (0.034)
pH = 1.5
What is the pH of 0.23M HCl?
pH = −log (0.23)
pH = −(−0.638)
pH = 0.64
Why is it important for the blood to be buffered to a pH between 7.35 and 7.45?
So the enzymes can function normally!
What other classes does Mrs. Torres teach this year?
Physics and Physics 1 AP
Consider the reaction
NH3(aq) + H2O(l) → NH4+(aq) + OH-(aq).
Which chemical is the conjugate acid?
The conjugate acid is NH4+
The CA is the base plus an H+
What is the [OH-] when the [H+] is 1.136 x 10-14 M?
(1.136 x 10-14)[OH-] = 1.0 x 10-14
[OH-] = 0.88 M
A solution has a [OH-] = 7.8x10-7, is it acidic, basic, or neutral?
pOH = 6.1
pH = 7.9
pH > 7, so basic!
What are the two things that a buffer solution needs to have to function?
A weak acid, and its conjugate base!
What is the animal for the Chinese zodiac for this year?
Snake
Consider the reaction
H2PO4-(aq) + H2O(l) → HPO42-(aq) + H3O+(aq)
Which chemical is the conjugate base?
The conjugate base is HPO42-(aq)
The CB is the acid minus an H+
What is the pOH for a solution with 0.078 M HNO3?
pH = -log(0.078) = 1.1
pOH = 14 - 1.1 = 12.9
What is the pH when there are 0.0078 moles of H+ in 5 liters of solution?
Molarity = 0.00156 M
pH = -log (0.00156)
pH = 2.8
I have a buffer solution with HCN (a weak acid) and NaCN (which is soluble in water). What happens when a small amount of [H+] enters this solution?
The CN- dissociates from the Na+ when in the water. The CN- will interact with the new H+, bonding with them to make HCN. In this way, the pH will not change much.
For our litmus paper lab, what was the color of a pH 8.5?
Green
How can water work as both an acid and a base in different chemical reactions?
Because water can give up a H+ and water can also lose an H+
What is the [OH-] for a solution with a pH of 4.9?
pOH = 14 - 4.9 = 9.1
[OH-] = 10-9.1
[OH-] = 7.9 x 10-10 M
What is the pOH of a solution with [H+] = 2.400 x 10-3 M?
pH = −log (2.4 x 10-3)
pH = 2.62
pOH = 14 - 2.62 = 11.38
A buffered solution contains hydrofluoric acid (HF). It also contains which of the following?
LiCl
H2SO4
KF
Ca(NO3)2
KF
HF is a weak acid, we need its conjugate base (which is F-)
For all five periods, how many students do Mr. Ma and Mrs. Torres teach?
32+33+31+33+29 = 158 students