Learning Goals
8.1
Learning Goals
8.2
Textbook Reading
“Chemistry: 2e” Second Edition, 2014. A digital version of the textbook will be available here.
Reading: Chapter 4 Section 2 and Chapter 14 Section 2
AP Daily Videos for 8.1
AP Daily Videos for 8.2
Extra Reference Sheet - pH Scale
Extra Reference Sheet - pH Scale
Quick Review
Whenever you have acid, you’ll also have a base.
An acid donates H+ ions (protons) to the base (proton acceptor).
Water is important to understand in acid-base chemistry.
Water acts as an acid and a base here, as it loses a proton to form OH- and gains a proton to form H3O+
Here the is Kw value discussed before.
[H3O+] and [OH-] must “balance out” to equal Kw (1x10-14)
If one goes up the other must go down.
Rearrange the Kw equation to solve for your unknown.
The first equation is what actually happens in the solution (Bronsted-Lowery acids and bases)
Note!
[H+] and [H3O+] mean the same thing! You’ll see them both ways on the AP exam.
Remember! As [H+] goes up, the pH value goes down!
Acidic solutions have low pH values (0-7) and basic solutions have high pH values (7-14).
Hold on! How can I “undo” a pH value into a concentration?!
This formula is NOT give on the AP Exam!
Hold on! How can I “undo” a pH value into a concentration?!
This formula is NOT given to you on the AP Exam!
Note! You cannot leave your answer in this format! Exponents must be whole numbers after your calculations are complete!
Hold on! How can I “undo” a pH value into a concentration?!
This formula is NOT given to you on the AP Exam!
Note! You cannot leave your answer in this format! Exponents must be whole numbers after your calculations are complete!
...
We can have negative numbers on the pH Scale!
0.1M HCl = pH 1
2M HCl = pH -0.3
B HBr Hydrobromic
I HI Hydroiodic
C HCl Hydrochloric
Pe HClO4 Perchloric
N HNO3 Nitric
S H2SO4 Sulfuric
Change the order in your notes!
BIC = monatomic acids
PeNS = polyatomic acids
Note! Sig Figs work differently with logarithms.
The rule states that the number of decimal places in the log is equal to the number of sig figs in the original number.
Note! Sig Figs work differently with logarithms.
The rule states that the number of decimal places in the log is equal to the number of sig figs in the original number.
Note! Sig Figs work differently with logarithms.
The rule states that the number of decimal places in the log is equal to the number of sig figs in the original number.
Note! Sig Figs work differently with logarithms.
The rule states that the number of decimal places in the log is equal to the number of sig figs in the original number.
We need to find the total amount of H3O+
Both HBr and HNO3 are strong acids that completely ionize.
So we need to find the [H3O+] in each solution then add them together with the new volume to find the new [H3O+]
We need to find the total amount of H3O+
Both HBr and HNO3 are strong acids that completely ionize.
So we need to find the [H3O+] in each solution then add them together with the new volume to find the new [H3O+]
Each acid will ionize and have a one to one ratio for H+ ions.
From HBr
From HNO3
Volumes are additive!!
Those two acids were in water! What about the water autoionizing?!
Let’s look at the connection between pH and pOH (the power of hydroxide!)
pOH = 0
pOH = 1
pOH = 2
pOH = 3
pOH = 4
pOH = 5
pOH = 6
pOH = 7
Like pH...
pOH is related to the [OH-]
pOH 7 = [OH-] of 1x10-7
pOH 6 = [OH-] of 1x10-6
pOH 5 = [OH-] of 1x10-5
Watch out!
You cannot jump directly from pH to [OH-]
pH + pOH = 14
This is on your equation sheet!
‘p’ means the ‘-log10’ of something so you can take the ‘p’ of anything.
Bases as proton acceptors, but many bases also contain OH- ions.
NH3 ammonia is also a common base.
Bases as proton acceptors, but many bases also contain OH- ions.
NH3 ammonia is also a common base.
Na+ always dissolves
K+ always dissolves
NH4+ always dissolves
NO3 always dissolves
You can have a negative pOH value as well.
pH + pOH = 14 is on your equation sheet!
pH focuses on [H+]
At higher temps Kw is higher so the [H+] is also higher. This DROPS the pH!
At lower temps Kw is lower so the [H+] is also lower. This RAISES the pH!
Learning Goals
8.1
Learning Goals
8.2
Homework
Evens!