Brad Ashburn, PhD Biochemistry 141

Module 14

Are all acids created equal?

2

Strong vs Weak

3

Strong vs Weak

4

Chemical Equilibrium

CO + H2O CO2 + H2

The forward reaction proceeds to the right.

The reverse reaction proceeds to the left.

5

The reaction is occurring in both directions simultaneously (equilibrium).

Chemical Equilibrium

6

Le Chatelier’s Principle

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The system will shift to oppose any change.

Le Chatelier’s Principles

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Concentration Change

9

2CO + O2 2CO2

If we increase the CO concentration

The equilibrium will shift to the right

The system will shift to oppose any change.

Concentration Change

10

2CO + O2 2CO2

If we increase the CO2 concentration

The equilibrium will shift to the left

The system will shift to oppose any change.

Concentration Change

11

2CO + O2 2CO2

If we decrease the CO2 concentration

The equilibrium will shift to the right

The system will shift to oppose any change.

Concept Check

12

Predict the direction of equilibrium when the

[Cl2] increases

[O2] decreases

[H2O] decreases

[HCl] increases

2Cl2 + 2H2O + heat 4HCl + O2

Measuring Acidity

13

Measuring Acidity

14

Calculating [H3O+] and [-OH]

15

The reaction of two water molecules:

Kw = [H3O+] x [-OH] = 1 x 10-14

16

The [H3O+] in a cup of Starbucks coffee is 1.0 x 10-5 M, calculate the [-OH].

Is this solution acidic or basic?

Concept Check

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Concept Check

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pH Scale

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neutralacidic basic

Lower pH Higher pH

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The pH of Body Fluids

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Significant Figures in pH Calculations

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Calculating pH from [H3O+]

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Given a solution with an [H3O+] of 1.2 x 10-5 M, calculate the pH?

pH = -log [H3O+]

24

Given a solution with an pH of 8.50, what is the [H3O+]?

pH = -log [H3O+]

Calculating [H3O+] from pH

The typical pH of human sweat is 6.8.What is the [H3O+]?

Buffers

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A buffer is a solution whose pH changes very little when acid or base is added.

Resists change in pH because:

added acid reacts with base

added base reacts with acid

Human Blood Buffer

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Normal blood pH is between 7.35-7.45

CO2 is constantly produced by metabolism of food

CO2 + H2O H2CO3 + H2O H3O+ + HCO3−

The [CO2] is directly related to the pH of the blood

Human Blood Buffer

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Normal blood pH is between 7.35-7.45

CO2 is constantly produced by metabolism of food

CO2 + H2O H2CO3 + H2O H3O+ + HCO3−

The [CO2] is directly related to the pH of the blood

Respiratory Acidosis

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Respiratory Alkalosis

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