Acid and Bases
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Acid and Bases
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Properties of an Acid
· Tastes sour· Turns blue litmus paper red
· Has a pH of less than 7· Lemon juice and vinegar are good examples.
ACID
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Properties of a Base · Turns litmus paper blue· Has a pH greater than 7· taste bitter and have a slippery feel
· Bases that are soluble (dissolve in water) are called alkalis
Most hand soaps and drain cleaners are bases
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p Hp H
A measure of how acidic something is
A measure of how acidic something is
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T h e p H S c a l eT h e p H S c a l e
• A N e u t r a l s o l u t i o n h a s a p H o f 7 .
• A n A c i d i c s o l u t i o n h a s a p H b e l o w 7 .
• A B a s i c s o l u t i o n h a s a p H a b o v e 7 .
• A N e u t r a l s o l u t i o n h a s a p H o f 7 .
• A n A c i d i c s o l u t i o n h a s a p H b e l o w 7 .
• A B a s i c s o l u t i o n h a s a p H a b o v e 7 .
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IndicatorsThese are chemicals that change colour in the presence of an acid or a base.
We get them from Plants.
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N e u t r a l i z a t i o nN e u t r a l i z a t i o n
T h e r e a c t i o n o f a n a c i d w i t h a b a s e t o p r o d u c e a s a l t a n d w a t e r .
When a fluid with a low pH (ACID) is mixed with a fluid with high pH (BASE) in the right proportions the two balance. The result is pH7 or NEUTRAL.
T h e r e a c t i o n o f a n a c i d w i t h a b a s e t o p r o d u c e a s a l t a n d w a t e r .
When a fluid with a low pH (ACID) is mixed with a fluid with high pH (BASE) in the right proportions the two balance. The result is pH7 or NEUTRAL.
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• Acid is added to BURRETTE
• Base is added to the conical flask using a pipette
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Initial Reading
Read the bottom of the meniscus to get starting point
Add indicator and base to the conical flask using a pipette
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Rough Titration
Due a quick titration to find approx value
Wash down the sides as you go along. No change in moles so no change in end point
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Use a white tile to see the end point clearly
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Titration Procedure
Then repeat this time the acid is slowly added to the base
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Final Reading
Do second slower swirling as you go
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N e u t r a l i z a t i o nR e a c t i o n sN e u t r a l i z a t i o nR e a c t i o n s
Acid + Base --> Salt + Water
H C l + N a O H --> N a C l + H 2 O
HNO 3 + NH4OH --> NH4NO 3 + H2O
Acid + Base --> Salt + Water
H C l + N a O H --> N a C l + H 2 O
HNO 3 + NH4OH --> NH4NO 3 + H2O
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Neutralisation
Acid + Base Salt + Water
We use an indictor (Substance that changes colour to show a chemical reaction has taken place). We may use Litmus or Methyl Orange. The experiment we do is:-
HCl + NaOH NaCl + H2OHydrochloric + Sodium Sodium + Water Acid Hydroxide Chloride
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Common examples of NEUTRALISATION
Sour apples +Antacid Calm Tummy + H2O
Conditioner +Shampoo Shiney Hair + H2O
Teeth +Toothpaste No Fillings + H2O
Bee Sting +Baking Soda Less pain + H2O
Vinegar +Wasp Sting No pain + H2O
Nettle +Doc Leaf Less Tears + H2O
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This lake looks ok, but it is dead
No fish life in this lake.
Acid rain kills trees and aquatic life.
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Emissions of sulfur dioxide and nitrogen oxides in tons/year
pH of rain in the USA
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All Acid rain is either caused by impurities or not burning fuel well.
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S + O2 SO2 (g)
This reaction occurs in combustion of sulfur rich coals in factories or in volcanoes
SO2 (g) + H2O (l) H2SO4 (l)
This reaction occurs in clouds
This acid rain then falls to the ground and enters the soil and water systems.
In areas where the bedrock is limestone (CaCO3) this acid rain is neutralized.
H2SO4 (l) + CaCO3 CO2 (g)+ CaSO4 (aq) + H2O (l)
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Summary
• Acids• Bases• Indicators• Neutralisation• Acid Rain
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H/W
• P223• Q 15-19