Acid and Bases

1. Acid and Bases

2. Acids • 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

3. Bases 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

4. p H A measure of how acidic something is

6. 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 .

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

8. 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.

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

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

12. 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

13. Use a white tile to see the end point clearly

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

15. Final Reading Do second slower swirling as you go

16. N 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

17. 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 + H2O Hydrochloric + Sodium Sodium + Water Acid Hydroxide Chloride

18. 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

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

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

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

22. 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. S + O2 SO2(g) This reaction occurs in combustion of sulfur rich coals in factories or in volcanoes In areas where the bedrock is limestone (CaCO3) this acid rain is neutralized. H2SO4(l) + CaCO3CO2(g)+ CaSO4(aq) + H2O (l)

23. Summary • Acids • Bases • Indicators • Neutralisation • Acid Rain

24. H/W • P223 • Q 15-19