 Explain the chemical composition of acids and bases, and explain the change of pH in neutralization reactions.

 I can differentiate between acids and bases.

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When dissolved in water, they ionize (form ions)
Form H + (Hydrogen) ions, which attach to water molecules to form hydronium ions, H
3
O +
Properties:

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
Taste sour
Blue litmus paper turns red
Conduct electric current
Corrosive

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Complete ionization in water
High concentration of hydronium ions in the liquid
Strong acid
Conducts electricity
Strong electrolyte

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Weak acids
Low concentration of hydronium ions in the liquid
Do not conduct electricity well
Weak electrolyte
Double headed arrow

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Corrosive
Can damage living tissues
Vapors can be harmful to eyes, mouth and lungs
Wear safety goggles, gloves, lab apron

 When dissolved in water form OH (hydroxide ions)
 Properties
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Tastes bitter
Solution feels slippery
Turn red litmus paper blue
Like acids, bases can also damage the skin

 When bases dissolve in water, they ionize.
NaOH Na + + OH -
 Not all bases contain OH -
 Some will react with water to form hydroxide ion
NH
3
+ H
2
O NH
4
+ + OH -

 High concentration of OH in the solution
Ba(OH)
2
Ba 2+
 Complete ionization in water
 Good conductor of electricity
 Strong electrolyte
+ 2OH -

 Low concentration of OH in solution
NH
3
+ H
2
O NH
4
+ + OH -
 Do not ionize completely
 Not a good conductor of electricity
 Weak electrolyte

 Bases are corrosive and can damage living tissue
 Wear safety goggles, gloves and a lab apron!!

 What ions do acids produce?
 What ions do bases produce?
 What is the difference between a strong acid and a weak acid?
 Why should we observe lab safety rules when working with acids and bases?

 I can explain pH.

 You can determine if a substance is an acid or a base by using an indicator.
 An indicator is a substance that changes color in the presence of an acid or base.
 Indicators measure the level of hydronium ions. The level determines if a substance is acidic or basic.

 Cabbage juice can be used as an indicator
 Litmus paper is a common indicator
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Acids turn blue litmus paper red
Bases turn red litmus paper blue
Only indicates if a substance is an acid or a base
 To determine strength or weakness, pH values are used catalog.flatworldknowledge.com
profmarsolais.com

 A measure of the concentration of H
3
O + ions in solution
 Acidity or basicity of a solution can be critical
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Enzymes in your body will not function properly if your blood is too basic or acidic
Fish cannot survive in waters that are too acidic or basic ck12.org
hapnotes.wikidot.com

Acid: substance that produces H + ions in aqueous solution
Base: substance that produces OH ions in aqueous solution
[H + ]
[OH ]
Stronger Weaker Weaker Stronger
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14
Acids pH Scale
Bases

• Small differences in pH mean large differences in acidity
• Example: pH of coke = 3 pH of coffee = 5
Coke is 10 2 , or 100, times more acidic than coffee.
ch302.cm.utexas.edu

gizmodo.com

Lemon juice has a pH of 2.2. Is it an acid or a base?

Detergents such as Tide have a pH of about 10.
Is Tide an acid or a base?

Seawater has a pH of 8.2. Is seawater an acid or a base?

The inside of your mouth has a pH of 7. Is it an acid or a base?

409 cleaner contains ammonia that has a pH of 12.
What will 409 do to red litmus paper?

A soft drink has a pH of 3.2.
What will it do to a piece of red litmus paper?

 You can find pH from the concentration of a strong acid.
 pH is the negative power of 10 that is used to describe the concentration of H
3
O + ions.
The concentration of H
3
O + in pure water is 1 x 10 -7 .
The pH of pure water = 7

 The concentration of H
3
O + ions in a solution of a strong acid is the same as the concentration of the acid.
 Determine the pH of a 0.0001 M (Molar) solution of the strong acid HCl.
concentration of H
3
O + ions = concentration of HCl concentration of H
3
O + ions = 0.0001 M = 1 x 10 -4 M pH = -(-4) = 4