pH Scale

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pH Scale
Soren Sorensen (1868 - 1939)
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pH Scale

Zumdahl, Zumdahl, DeCoste, World of Chemistry
2002, page 515
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pH of Common Substances
Timberlake, Chemistry 7th Edition, page 335
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pH of Common Substance
pH H1 OH1- pOH
14 1 x 10-14 1 x 10-0 0 13 1 x
10-13 1 x 10-1 1 12 1 x 10-12
1 x 10-2 2 11 1 x 10-11 1 x 10-3
3 10 1 x 10-10 1 x 10-4 4
9 1 x 10-9 1 x 10-5 5 8 1 x
10-8 1 x 10-6 6 6 1 x 10-6
1 x 10-8 8 5 1 x 10-5 1 x 10-9
9 4 1 x 10-4 1 x 10-10 10
3 1 x 10-3 1 x 10-11 11 2 1 x 10-2
1 x 10-12 12 1 1 x 10-1 1 x
10-13 13 0 1 x 100 1 x 10-14 14
NaOH, 0.1 M Household bleach Household
ammonia Lime water Milk of magnesia Borax Bakin
g soda Egg white, seawater Human blood,
tears Milk Saliva Rain Black coffee Banana Tomato
es Wine Cola, vinegar Lemon juice Gastric juice
More basic
7 1 x 10-7 1 x 10-7 7
More acidic
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Acid Base Concentrations
10-1
pH 3
pH 11
OH-
H3O
pH 7
10-7
concentration (moles/L)
OH-
H3O
OH-
H3O
10-14
H3O lt OH-
H3O OH-
H3O gt OH-
acidic solution
neutral solution
basic solution
Timberlake, Chemistry 7th Edition, page 332
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pH
pH -log H1
Kelter, Carr, Scott, Chemistry A World of Choices
1999, page 285
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pH Calculations
pH
H3O
pH -logH3O
H3O 10-pH
pH pOH 14
H3O OH- 1 x10-14
pOH
OH-
pOH -logOH-
OH- 10-pOH
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pH - log H
Given
determine the hydronium ion
pH 4.6
choose proper equation
pH - log H
substitute pH value in equation
4.6 - log H
multiply both sides by -1
- 4.6 log H
take antilog of both sides
- 4.6 log H
H 2.51x10-5 M
Recall, H H3O
You can check your answer by working backwards.
pH - log H
pH - log 2.51x10-5 M
pH 4.6
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pH and pOH Calculations
        pH and pOH Calculations
        pH and pOH Calculations
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Acid Dissociation
pH ?
pH - log H
H1(aq) A1-(aq)
HA(aq)
monoprotic
0.3 M
0.3 M
0.3 M
pH - log 3M
e.g. HCl, HNO3
pH - 0.48
pH - log H
2 H1(aq) A2-(aq)
H2A(aq)
diprotic
0.3 M
0.6 M
0.3 M
pH - log 6M
e.g. H2SO4
pH - 0.78
Given pH 2.1
3 H1(aq) PO43-(aq)
polyprotic
H3PO4(aq)
e.g. H3PO4
? M
x M
find H3PO4
assume 100 dissociation
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Given pH 2.1
3 H1(aq) PO43-(aq)
H3PO4(aq)
X M
0.00794 M
find H3PO4
assume 100 dissociation
Step 1) Write the dissociation of phosphoric acid
Step 2) Calculate the H concentration
pH - log H
2.1 - log H
H 10-pH
- 2.1 log H
H 10-2.1
H 0.00794 M
7.94 x10-3 M
H 7.94 x10-3 M
Step 3) Calculate H3PO4 concentration
Note coefficients (13) for (H3PO4 H)

0.00265 M H3PO4
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How many grams of magnesium hydroxide are needed
to add to 500 mL of H2O to yield a pH of 10.0?
Mg2
OH1-
Step 1) Write out the dissociation of magnesium
hydroxide
Mg(OH)2
Mg(OH)2(aq)
Mg2(aq)
2 OH1-(aq)

1 x10-4 M
0.5 x10-4 M
5 x10-5 M
pH pOH 14
Step 2) Calculate the pOH
10.0 pOH 14
pOH 4.0
pOH - log OH1-
Step 3) Calculate the OH1-
OH1- 10-OH
OH1- 1 x10-4 M
Step 4) Solve for moles of Mg(OH)2
x 2.5 x 10-5 mol Mg(OH)2
Step 5) Solve for grams of Mg(OH)2
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Practice Problems - Key
        Practice Problems - Answer Key
        Practice Problems - Answer Key