Acid and Bases

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

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

p H A measure of how acidic something is

T 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.

Indicators These are chemicals that change colour in the presence of an acid or a base. We get them from Plants.

N 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.

Acid is added to BURRETTE Base is added to the conical flask using a pipette

Initial Reading Read the bottom of the meniscus to get starting point Add indicator and base to the conical flask using a pipette

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

Use a white tile to see the end point clearly

Titration Procedure Then repeat this time the acid is slowly added to the base

Final Reading Do second slower swirling as you go

N e u t r a l i z a t i o n R 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 + NH 4 OH --> NH 4 NO 3 + H 2 O Acid + Base --> Salt + Water H C l + N a O H --> N a C l + H 2 O HNO 3 + NH 4 OH --> NH 4 NO 3 + H 2 O

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 + H 2 O Hydrochloric + Sodium  Sodium + Water Acid Hydroxide Chloride

Common examples of NEUTRALISATION Sour apples +Antacid  Calm Tummy + H 2 O Conditioner +Shampoo  Shiney Hair + H 2 O Teeth +Toothpaste  No Fillings + H 2 O Bee Sting +Baking Soda  Less pain + H 2 O Vinegar +Wasp Sting  No pain + H 2 O Nettle +Doc Leaf  Less Tears + H 2 O

This lake looks ok, but it is dead No fish life in this lake. Acid rain kills trees and aquatic life.

Emissions of sulfur dioxide and nitrogen oxides in tons/year pH of rain in the USA

All Acid rain is either caused by impurities or not burning fuel well.

S + O 2  SO 2 (g) This reaction occurs in combustion of sulfur rich coals in factories or in volcanoes SO 2 (g) + H 2 O (l)  H 2 SO 4 (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 (CaCO 3 ) this acid rain is neutralized. H 2 SO 4 (l) + CaCO 3  CO 2 (g) + CaSO 4 (aq) + H 2 O (l)

Summary Acids Bases Indicators Neutralisation Acid Rain

H/W P223 Q 15-19