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Acids and Bases
What are these?
Lemon CokeVinegar
What is an Acid?
 An acid is a substance that produces
hydrogen ions, H+
in water.
 An acid therefore can conduct
electr...
What are these?
Window Cleaner Floor Cleaner Baking Soda
What is an Alkali?
 An alkali is a substance that produces
hydroxide ions, OH-
in water.
 An alkali can conduct electric...
Examples of Acids
Names of acids Chemical formula Where can it be found?
Hydrochloric acid HCl In gastric juice in the sto...
Acidic or not?
Chemical name Name of
compound
Is it
Acidic?
H2SO4 (aq) Sulphuric acid Yes
HNO3 (aq) Nitric acid Yes
CH3COO...
Strength of an Acid
 The strength of an acid depends on the
extent of ionisation.
 The acid is stronger when more molecu...
Strong Acids
: acid molecule : acid ions
_
+
_
_
_
_
+
+
+
+
_
+
Dissolved in
water
Strong Acids
 A strong acid is one in which all the acid
molecules become ions in water.
 Examples: Hydrochloric acid, H...
Weak Acids
: acid molecule : acid ions
_
+
_
+
Dissolved in
water
Weak Acids
 A weak acid is one in which only a few acid
molecules become ions in water.
 Examples: Acetic acid, CH3COOH ...
Reaction of Acids with
Metals
 General Equation:
Metal + Acid  Salt + Hydrogen gas
 Observation:
The metal dissolves
an...
Reaction of Acids with
Metals
 Mg(s) + 2HCl(aq) →
Magnesium + Hydrochloric
acid
→
 Ca(s) + H2SO4 (aq) →
Calcium + Sulphu...
Reaction of Acids with
Carbonates
 General Equation:
Metal + Acid  Salt + Water + Carbon
Carbonate dioxide
gas
Reaction of Acids with
Carbonates
 Observation:
The metal dissolve and effervescence
occurs. The gas forms a white precip...
Reaction of Acids with
Carbonates
 MgCO3 (s) + 2HCl(aq) →
Magnesium +
carbonate
Hydrochloric
acid
→
 → CaSO4(aq) + H2O(l...
Reaction of Acids with
Alkalis
 General Equation:
Alkali + Acid  Salt + Water
Reaction of Acids with
Bases
 Base: Metal oxides, Metal hydroxides
 NaOH + HCl 
 KOH + H2SO4 
Sodium
hydroxide
Hydroc...
Uses of Acids
Acids
Preserving food
-acetic acid in
vinegar
Making industrial
products
-nitric acid in
fertilisers
-sulphu...
Complete the Puzzle
Across
1. Acids react with _______ to give salt and water
only.
5. Only _______ solution of acids have...
Answer
Across
1. Acids react with bases to give
salt and water only.
5. Only aqueous solution of acids
have acidic propert...
Answer
Down
2. Sulphuric acid is an example of a
strong acid which is found in car
battery.
3. Carbonates react with acids...
Summary
 An acid is a substance that produces
hydrogen ions in water.
 Only an aqueous solution of acid has acidic
prope...
Summary
 An acid
- pH < 7
- turn blue litmus paper red.
- taste sour
- stinging feeling
- is corrosive (for strong acids)...
Summary
 Reactions of acids with
1. metals
Metal + Acid  Salt + Hydrogen gas
2. carbonates
Metal + Acid  Salt + Water +...
Summary
 An alkali
- pH > 7
- turn red litmus paper blue
- taste bitter
- caustic
- is corrosive (for strong alkalis)
- c...
pH Indicators
 Methyl orange:
pH Indicators
 Universal Indicator
pH Indicators
 Phenolphthalein
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Acids and Bases

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Acids and Bases

  1. 1. Acids and Bases
  2. 2. What are these? Lemon CokeVinegar
  3. 3. What is an Acid?  An acid is a substance that produces hydrogen ions, H+ in water.  An acid therefore can conduct electricity.  pH < 7  It has a sour taste.  It has a stinging feeling.  It is corrosive.
  4. 4. What are these? Window Cleaner Floor Cleaner Baking Soda
  5. 5. What is an Alkali?  An alkali is a substance that produces hydroxide ions, OH- in water.  An alkali can conduct electricity.  pH > 7  It has a bitter taste.  It is caustic.  It is corrosive.
  6. 6. Examples of Acids Names of acids Chemical formula Where can it be found? Hydrochloric acid HCl In gastric juice in the stomach Sulphuric acid H2SO4 In car battery Nitric acid HNO3 In the preparation of fertilizers and explosives Carbonic acid H2CO3 In fizzy drinks Citric acid C6H8O7 In oranges and lemons Acetic acid CH3COOH In vinegar
  7. 7. Acidic or not? Chemical name Name of compound Is it Acidic? H2SO4 (aq) Sulphuric acid Yes HNO3 (aq) Nitric acid Yes CH3COOH(aq) Ethanoic acid/acetic acid Yes H2O (s) water No
  8. 8. Strength of an Acid  The strength of an acid depends on the extent of ionisation.  The acid is stronger when more molecules are ionised.
  9. 9. Strong Acids : acid molecule : acid ions _ + _ _ _ _ + + + + _ + Dissolved in water
  10. 10. Strong Acids  A strong acid is one in which all the acid molecules become ions in water.  Examples: Hydrochloric acid, HCl (aq) Sulphuric acid, H2SO4 (aq) Nitric acid, HNO3 (aq)
  11. 11. Weak Acids : acid molecule : acid ions _ + _ + Dissolved in water
  12. 12. Weak Acids  A weak acid is one in which only a few acid molecules become ions in water.  Examples: Acetic acid, CH3COOH (aq) Citric acid, C6H8O7(aq) Carbonic acid, H2CO3(aq)
  13. 13. Reaction of Acids with Metals  General Equation: Metal + Acid  Salt + Hydrogen gas  Observation: The metal dissolves and effervescence occurs. The gas extinguishes a burning splint with a ‘pop’ sound.
  14. 14. Reaction of Acids with Metals  Mg(s) + 2HCl(aq) → Magnesium + Hydrochloric acid →  Ca(s) + H2SO4 (aq) → Calcium + Sulphuric acid →  Zn (s) + H2SO4 (aq) → ZnSO4(aq) + H2(g) → Zinc + sulphate Hydrogen gas MgCl2 (aq) + H2 (g) Magnesium chloride + hydrogen gas CaSO4 (aq) + H2 (g) Calcium sulphate + hydrogen gas Zinc + sulphuric acid
  15. 15. Reaction of Acids with Carbonates  General Equation: Metal + Acid  Salt + Water + Carbon Carbonate dioxide gas
  16. 16. Reaction of Acids with Carbonates  Observation: The metal dissolve and effervescence occurs. The gas forms a white precipitate with limewater.
  17. 17. Reaction of Acids with Carbonates  MgCO3 (s) + 2HCl(aq) → Magnesium + carbonate Hydrochloric acid →  → CaSO4(aq) + H2O(l) + CO2(g) Calcium + sulphate Water +→ Carbon dioxide gas MgCl2 (aq) + H2O (l)+ CO2(g) Magnesium chloride + water + carbon dioxide CaCO3 (s) + H2SO4 (aq) Calcium + sulphuric Carbonate acid
  18. 18. Reaction of Acids with Alkalis  General Equation: Alkali + Acid  Salt + Water
  19. 19. Reaction of Acids with Bases  Base: Metal oxides, Metal hydroxides  NaOH + HCl   KOH + H2SO4  Sodium hydroxide Hydrochloric acid Potassium hydroxide Sulphuric acid + + + +→ → NaCl (aq) + H2O (l) Sodium chloride water K2SO4 (aq) + H2O (l) Potassium sulphate water
  20. 20. Uses of Acids Acids Preserving food -acetic acid in vinegar Making industrial products -nitric acid in fertilisers -sulphuric acid in detergents Rust removal from iron and steel -Sulphuric acid -Hydrochloric acid Car battery -Sulphuric acid
  21. 21. Complete the Puzzle Across 1. Acids react with _______ to give salt and water only. 5. Only _______ solution of acids have acidic properties. 6. In a strong acid, the acid molecules are _______ ionised. 8. Ethanoic acid is an example of a _______ acid. 9. Acids have a _______ taste. Down 2. _______ acid is an example of a strong acid which is found in car battery. 3. _______ react with acids to give off a gas that forms a white precipitate with limewater. 4. When dissolved in water, acid molecules can ionise to give _______ ions. 7. Hydrogen gas is evolved when acids react with _______.
  22. 22. Answer Across 1. Acids react with bases to give salt and water only. 5. Only aqueous solution of acids have acidic properties. 6. In a strong acid, the acid molecules are completely ionised. 8. Ethanoic acid is an example of a weak acid. 9. Acids have a sour taste.
  23. 23. Answer Down 2. Sulphuric acid is an example of a strong acid which is found in car battery. 3. Carbonates react with acids to give off a gas that forms a white precipitate with limewater. 4. When dissolved in water, acid molecules can ionise to give hydrogen ions. 7. Hydrogen gas is evolved when acids react with metals.
  24. 24. Summary  An acid is a substance that produces hydrogen ions in water.  Only an aqueous solution of acid has acidic properties. HCl (aq)  H+ (aq) + Cl- (aq)  The greater the extent of ionisation, the stronger the acid.
  25. 25. Summary  An acid - pH < 7 - turn blue litmus paper red. - taste sour - stinging feeling - is corrosive (for strong acids) - can conduct electricity.
  26. 26. Summary  Reactions of acids with 1. metals Metal + Acid  Salt + Hydrogen gas 2. carbonates Metal + Acid  Salt + Water + Carbon Carbonate dioxide gas 3. bases Base + Acid  Salt + Water
  27. 27. Summary  An alkali - pH > 7 - turn red litmus paper blue - taste bitter - caustic - is corrosive (for strong alkalis) - can conduct electricity.
  28. 28. pH Indicators  Methyl orange:
  29. 29. pH Indicators  Universal Indicator
  30. 30. pH Indicators  Phenolphthalein

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