Section 6.3—Acidity, pH
description
Transcript of Section 6.3—Acidity, pH
![Page 1: Section 6.3—Acidity, pH](https://reader030.fdocuments.in/reader030/viewer/2022033022/5681645d550346895dd62f59/html5/thumbnails/1.jpg)
Section 6.3—Acidity, pH
How does concentration of acid affect the pH of a sports drink?
![Page 2: Section 6.3—Acidity, pH](https://reader030.fdocuments.in/reader030/viewer/2022033022/5681645d550346895dd62f59/html5/thumbnails/2.jpg)
A Review of Acids & Bases
![Page 3: Section 6.3—Acidity, pH](https://reader030.fdocuments.in/reader030/viewer/2022033022/5681645d550346895dd62f59/html5/thumbnails/3.jpg)
Acids – Arrhenius Definition
Produce Hydronium ion (H3O+1) in waterHydronium ion is water + a hydrogen
cation
HO
H
water
H+1
HO
H
H +1
By this definition, if an acid is to give a H+1 to water, then all acids will have hydrogen as the cation (first element written).
![Page 4: Section 6.3—Acidity, pH](https://reader030.fdocuments.in/reader030/viewer/2022033022/5681645d550346895dd62f59/html5/thumbnails/4.jpg)
How do Acids produce Hydronium?
HO
H
H -
water acid
Hydrogen cation with some anion
![Page 5: Section 6.3—Acidity, pH](https://reader030.fdocuments.in/reader030/viewer/2022033022/5681645d550346895dd62f59/html5/thumbnails/5.jpg)
How do Acids produce Hydronium?
HO
H
H -+1
![Page 6: Section 6.3—Acidity, pH](https://reader030.fdocuments.in/reader030/viewer/2022033022/5681645d550346895dd62f59/html5/thumbnails/6.jpg)
How do Acids produce Hydronium?
HO
H
H+1 -
Hydronium ion Anion
![Page 7: Section 6.3—Acidity, pH](https://reader030.fdocuments.in/reader030/viewer/2022033022/5681645d550346895dd62f59/html5/thumbnails/7.jpg)
Bases – Arrhenius Definition
Bases produce the hydroxide ion in water
HO-1
Hydroxide Ion
![Page 8: Section 6.3—Acidity, pH](https://reader030.fdocuments.in/reader030/viewer/2022033022/5681645d550346895dd62f59/html5/thumbnails/8.jpg)
Characteristics of Acids & Bases
BasesAcids
Produce H3O+1 (hydronium ion) in water
Produce OH-1 (hydroxide ion) in water
Tastes sour Tastes Bitter
React with active metals to form hydrogen gas Feels slippery
![Page 9: Section 6.3—Acidity, pH](https://reader030.fdocuments.in/reader030/viewer/2022033022/5681645d550346895dd62f59/html5/thumbnails/9.jpg)
Strength versus Concentration
![Page 10: Section 6.3—Acidity, pH](https://reader030.fdocuments.in/reader030/viewer/2022033022/5681645d550346895dd62f59/html5/thumbnails/10.jpg)
Strong versus Weak Acids
+
++
-
-
-
Strong acidMost of the acid molecules
have donated the H+1 to water
How many hydronium ion – anion pairs can you find?
How many intact acid molecules can you find?
3
1
![Page 11: Section 6.3—Acidity, pH](https://reader030.fdocuments.in/reader030/viewer/2022033022/5681645d550346895dd62f59/html5/thumbnails/11.jpg)
Strong versus Weak Acids
+
-
Weak acidOnly a few of the acid
molecules have donated the H+1 to water
How many hydronium ion – anion pairs can you find?
How many intact acid molecules can you find?
1
3
![Page 12: Section 6.3—Acidity, pH](https://reader030.fdocuments.in/reader030/viewer/2022033022/5681645d550346895dd62f59/html5/thumbnails/12.jpg)
Concentrated versus Dilute
solute solvent
Lower concentration
Not as many solute (what’s being dissolved) particles
Higher concentration
More solute (what’s being dissolved) particles
![Page 13: Section 6.3—Acidity, pH](https://reader030.fdocuments.in/reader030/viewer/2022033022/5681645d550346895dd62f59/html5/thumbnails/13.jpg)
Combinations of Concentration & Strength
DiluteConcentrated
A lot of acid added & most
dissociates
Not much acid added, but most of
what’s there dissociates
A lot of acid added, but most stays together
Not much acid added and most of what is there stays
together
Strong
Weak
![Page 14: Section 6.3—Acidity, pH](https://reader030.fdocuments.in/reader030/viewer/2022033022/5681645d550346895dd62f59/html5/thumbnails/14.jpg)
Acids and Bases as Electrolytes
Acids and bases dissociate into ions in water
Free-floating ions in water conduct electricity
Acids & Bases are electrolytes
Strong acids and bases are strong electrolytesWeak acids and bases are weak electrolytes
![Page 15: Section 6.3—Acidity, pH](https://reader030.fdocuments.in/reader030/viewer/2022033022/5681645d550346895dd62f59/html5/thumbnails/15.jpg)
pH
![Page 16: Section 6.3—Acidity, pH](https://reader030.fdocuments.in/reader030/viewer/2022033022/5681645d550346895dd62f59/html5/thumbnails/16.jpg)
Is a scale to measure the acidity of a sample
pH Scale
1 14
Highly acidic Very basic (not acidic)
neutral
7
Chapter 6 will give more detail about how pH is calculated!
![Page 17: Section 6.3—Acidity, pH](https://reader030.fdocuments.in/reader030/viewer/2022033022/5681645d550346895dd62f59/html5/thumbnails/17.jpg)
pH is a Logarithmic Scale
Logarithm –The number of times a base must be multiplied by itself to reach a given number
yx blog# of multiples
Base
# you’re trying to reach
![Page 18: Section 6.3—Acidity, pH](https://reader030.fdocuments.in/reader030/viewer/2022033022/5681645d550346895dd62f59/html5/thumbnails/18.jpg)
Calculating pH
pH scale – Logarithmic scale of the acidity of a solution
The pH scale uses base “10”
]log[ 13
OHpH
pHOH 10][ 13
pH has not units
[ ] = concentration in Molarity
![Page 19: Section 6.3—Acidity, pH](https://reader030.fdocuments.in/reader030/viewer/2022033022/5681645d550346895dd62f59/html5/thumbnails/19.jpg)
The “-” in the pH equation
Concentration of Hydronium ion versus pH
0
0.5
1
0 0.5 1 1.5 2
pH
[H3O
+]
Because pH is the negative log of concentration of hydronium, as concentration increases, the pH goes down.
The lowest pH is the highest concentration of hydronium
![Page 20: Section 6.3—Acidity, pH](https://reader030.fdocuments.in/reader030/viewer/2022033022/5681645d550346895dd62f59/html5/thumbnails/20.jpg)
What does a “log” scale really mean?
pH
4
3
2
1
10x more acidic
100x more acidic
1000x more acidic
Leve
l of a
cidi
ty in
crea
ses
Every change of 1 in pH shows a change of 10x in concentration of hydronium
![Page 21: Section 6.3—Acidity, pH](https://reader030.fdocuments.in/reader030/viewer/2022033022/5681645d550346895dd62f59/html5/thumbnails/21.jpg)
An example of calculating pH
Example:Find the pH if the concentration of [H3O+1] is 0.25 M
![Page 22: Section 6.3—Acidity, pH](https://reader030.fdocuments.in/reader030/viewer/2022033022/5681645d550346895dd62f59/html5/thumbnails/22.jpg)
An example of calculating pH
pH = 0.60
]log[ 13
OHpH
)25.0log( MpH
Example:Find the pH if the concentration of [H3O+1] is 0.25 M
![Page 23: Section 6.3—Acidity, pH](https://reader030.fdocuments.in/reader030/viewer/2022033022/5681645d550346895dd62f59/html5/thumbnails/23.jpg)
An example of calculating hydronium
Example:Find the [H3O+1] if
the pH is 2.7
![Page 24: Section 6.3—Acidity, pH](https://reader030.fdocuments.in/reader030/viewer/2022033022/5681645d550346895dd62f59/html5/thumbnails/24.jpg)
An example of calculating hydronium
H3O+1 = 0.0020 M
pHOH 10][ 13
7.213 10][ OH
Example:Find the [H3O+1] if
the pH is 2.7
![Page 25: Section 6.3—Acidity, pH](https://reader030.fdocuments.in/reader030/viewer/2022033022/5681645d550346895dd62f59/html5/thumbnails/25.jpg)
Auto-ionization of Water
Water will split into ions 2 H2O H3O+1 + OH-1
Water will do this to make sure that at 25°C the following is true:[H3O+1] × [OH-1] = 1 × 10-14
So if you know the hydronium concentration at 25°C (which can be found from pH), then you can also find the hydroxide concentration
![Page 26: Section 6.3—Acidity, pH](https://reader030.fdocuments.in/reader030/viewer/2022033022/5681645d550346895dd62f59/html5/thumbnails/26.jpg)
An example of calculating hydroxide
Example:Find the [OH-1] if the pH is 10.7
![Page 27: Section 6.3—Acidity, pH](https://reader030.fdocuments.in/reader030/viewer/2022033022/5681645d550346895dd62f59/html5/thumbnails/27.jpg)
An example of calculating hydroxide
14113 101][][ OHOH
14111 101][]100.2[ OH
Example:Find the [OH-1] if the pH is 10.7
H3O+1 = 2.0 × 10-11 M
pHOH 10][ 13
7.1013 10][ OH
]100.2[101][ 11
141
OHOH-1 = 0.0005 M
![Page 28: Section 6.3—Acidity, pH](https://reader030.fdocuments.in/reader030/viewer/2022033022/5681645d550346895dd62f59/html5/thumbnails/28.jpg)
Let’s Practice #1
Example:Find the pH if the concentration of
[H3O+1] is 2.5 × 10-5 M
![Page 29: Section 6.3—Acidity, pH](https://reader030.fdocuments.in/reader030/viewer/2022033022/5681645d550346895dd62f59/html5/thumbnails/29.jpg)
Let’s Practice #1
pH = 4.6
]log[ 13
OHpH
)105.2log( 5MpH
Example:Find the pH if the concentration of
[H3O+1] is 2.5 × 10-5 M
![Page 30: Section 6.3—Acidity, pH](https://reader030.fdocuments.in/reader030/viewer/2022033022/5681645d550346895dd62f59/html5/thumbnails/30.jpg)
Let’s Practice #2
Example:Find the [OH-1] if
the pH is 3.6
![Page 31: Section 6.3—Acidity, pH](https://reader030.fdocuments.in/reader030/viewer/2022033022/5681645d550346895dd62f59/html5/thumbnails/31.jpg)
Let’s Practice #2
14113 101][][ OHOH
1414 101][]105.2[ OH
Example:Find the [OH-1] if
the pH is 3.6
H3O+1 = 2.5 × 10-4 M
pHOH 10][ 13
6.313 10][ OH
]105.2[101][ 4
141
OHOH-1 = 4.0 ×10-11 M
![Page 32: Section 6.3—Acidity, pH](https://reader030.fdocuments.in/reader030/viewer/2022033022/5681645d550346895dd62f59/html5/thumbnails/32.jpg)
Let’s Practice #3
Example:Find the [H3O+1] if
the pH is 11.2
![Page 33: Section 6.3—Acidity, pH](https://reader030.fdocuments.in/reader030/viewer/2022033022/5681645d550346895dd62f59/html5/thumbnails/33.jpg)
Let’s Practice #3
H3O+1 = 6.3 × 10-12 M
pHOH 10][ 13
2.1113 10][ OH
Example:Find the [H3O+1] if
the pH is 11.2