1. Bases Who's on first?

2. Back to Our Color-Coded Scale What about the right-hand side of this?

3. Some Questions 1. If pH comes from [H + ], how do you have a pH in base, which doesn't have any H+? 2. What makes something a base in the first place?

4. Once Again, in Reverse 2. What makes something a base in the first place? Arrhenius: makes OH - when put in water Bronsted: gets an H + Two ways to make OH - in water:

5. Once Again, in Reverse 2. What makes something a base in the first place? Arrhenius: makes OH - when put in water Bronsted: gets an H + Two ways to make OH - in water: 1. Just put some hydroxide in!NaOH, or Ca(OH) 2, or KOH... (note: these must be ionic, or it's not really OH -. CH 3 OH is not a base)

6. Once Again, in Reverse 2. What makes something a base in the first place? Arrhenius: makes OH - when put in water Bronsted: gets an H + Two ways to make OH - in water: 1. Just put some hydroxide in!NaOH, or Ca(OH) 2, or KOH... (note: these must be ionic, or it's not really OH -. CH 3 OH is not a base) 2. Pull an H + off water to turn it into OH - : B - (aq) + H 2 O (l) → HB (aq) + OH - (aq)

7. Strong vs Weak 2. Pull an H + off water to turn it into OH - : B - (aq) + H 2 O (l) → HB (aq) + OH - (aq) Just like with acids, you can have strong and weak bases. Strong ones do this reaction 100% Common strong bases:OH -, O 2-, H -, and NH 2 -

8. Strong vs Weak 2. Pull an H + off water to turn it into OH - : B - (aq) + H 2 O (l) → HB (aq) + OH - (aq) Just like with acids, you can have strong and weak bases. Strong ones do this reaction 100% Common strong bases:OH -, O 2-, H -, and NH 2 - There's one tricky thing with oxide, though, if we write the equation out: O 2- (aq) + H 2 O (l) → OH - (aq) + OH - (aq) You end up with two hydroxides. This will be relevant later.

9. Back to Question 1 1. If pH comes from [H + ], how do you have a pH in base, which doesn't have any H + ? This goes back to the acids video:[H + ]*[OH - ] = 10 -14 While both are 10 -7 M for neutral water, this equation is always true. So if we add a bunch of base, the [OH - ] will be higher, so [H + ] wil be lower. Example:0.1 M NaOH[OH - ] = 0.1 M [H + ]*0.1 = 10 -14 [H + ] = 10 -13 pH = -log(10 -13 ) = 13

10. A “Shortcut” Method Example:0.1 M NaOH[OH - ] = 0.1 M [H + ]*0.1 = 10 -14 [H + ] = 10 -13 pH = -log(10 -13 ) = 13 If we define pOH to be like pH:pOH = -log[OH - ] Then using some algebra, we get:pH + pOH = 14 So back to the same example: 0.1 M NaOH[OH - ] = 0.1 M pOH = -log(0.1) = 1pH + 1 = 14pH = 13

11. Two places where you can run into trouble: 1. Some hydroxide compounds have more than one hydroxide: If I make 0.1 M Ca(OH) 2, the [OH - ] = 0.2 M 2. Remember the thing about oxides? This is where it comes up” If I make 0.1 M Na 2 O, the [OH - ] = 0.2 M

12. Summary Bases make OH - in water, either by being OH -, or getting an H + Strong bases completely pull H + off water OH -, O 2-, H -, and NH 2 - are the most common strong bases pOH = -log[OH - ] Use pH + pOH = 14 or [H + ]*[OH - ] = 10 -14 to get pH BASE jumping is something else entirely.