Acids and Bases

What are these? Lemon Coke Vinegar Acids

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 .

What are these? Window Cleaner Floor Cleaner Baking Soda Bases

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 .

Examples of Acids I n the preparation of fertilizers and explosives HNO 3 Nitric acid In fizzy drinks H 2 CO 3 Carbonic acid In oranges and lemons C 6 H 8 O 7 Citric acid In vinegar CH 3 COOH Acetic acid In car battery H 2 SO 4 Sulphuric acid In gastric juice in the stomach HCl Hydrochloric acid Where can it be found? Chemical formula Names of acids

Acidic or not? Yes Nitric acid HNO 3 (aq) No water H 2 O (s) Yes Ethanoic acid/acetic acid CH 3 COOH(aq) Yes Sulphuric acid H 2 SO 4 (aq) Is it Acidic? Name of compound Chemical name

Strength of an Acid
The strength of an acid depends on the extent of ionisation .
The acid is stronger when more molecules are ionised.

Strong Acids : acid molecule Dissolved in water : acid ions _ + _ _ _ _ + + + + _ +

Strong Acids
A strong acid is one in which all the acid molecules become ions in water.
Examples: Hydrochloric acid, HCl (aq)
Sulphuric acid, H 2 SO 4 (aq)
Nitric acid, HNO 3 (aq)

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, CH 3 COOH (aq)
Citric acid, C 6 H 8 O 7 (aq)
Carbonic acid, H 2 CO 3 (aq)

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.

Reaction of Acids with Metals
Mg(s) + 2HCl(aq) 
Ca (s) + H 2 SO 4 (aq) 
Zn (s) + H 2 SO 4 (aq)  ZnSO 4 (aq) + H 2 (g)
MgC l 2 (aq) + H 2 (g) Magnesium chloride + hydrogen gas CaSO 4 (aq) + H 2 (g) Calcium sulphate + hydrogen gas Zinc + sulphuric acid Magnesium + H ydrochloric acid  Calcium + Sulphuric acid   Zinc + sulphate
H ydrogen
gas

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 precipitate with limewater.

Reaction of Acids with Carbonates MgC l 2 (aq) + H 2 O (l)+ CO 2 (g) Magnesium chloride + water + carbon dioxide CaCO 3 (s) + H 2 SO 4 (aq) Calcium + sulphuric Carbonate acid
MgC O 3 (s) + 2HCl(aq) 
Magnesium + carbonate H ydrochloric acid 
 CaSO 4 (aq) + H 2 O ( l ) + CO 2 ( g )
Calcium + sulphate
Water +

Carbon
dioxide
gas

Reaction of Acids with Alkalis
General Equation:
Alkali + Acid  Salt + Water

Reaction of Acids with Bases
Base: Metal oxides, Metal hydroxides
NaOH + HCl 
KOH + H 2 SO 4 
Sodium hydroxide Hydrochloric acid Potassium hydroxide Sulphuric acid + + + +   NaC l (aq) + H 2 O (l) Sodium chloride water K 2 SO 4 (aq) + H 2 O (l) Potassium sulphate water

Uses of Acids Acids Preserving food -acetic acid in vinegar M aking industrial products -nitric acid in fertilisers -sulphuric acid in detergents Rust removal from iron and steel -Sulphuric acid -Hydrochloric acid Car battery -Sulphuric acid

Complete the Puzzle
Across
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 reac t with _______.

Answer
Across
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 completel y ionised.
8. Ethanoic acid is an example of a weak acid.
9. Acids have a sour taste.

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 reac t with metals .

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.

Summary
An acid
- pH < 7
- turn blue litmus paper red.
- taste sour
- stinging feeling
- is corrosive (for strong acids)
- can conduct electricity.

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

Summary
An alkali
- pH > 7
- turn red litmus paper blue
- taste bitter
- caustic
- is corrosive (for strong alkalis)
- can conduct electricity.

pH Indicators
Methyl orange:

pH Indicators
Universal Indicator

pH Indicators
Phenolphthalein

http://chemclass4spm.blogspot.com	8814
http://sirazlee.blogspot.com	1702
https://klearning.ict.kis.ac.th	641
http://www.chemclass4spm.blogspot.com	45
http://www.slideshare.net	15
http://wei-han-betty32g.blogspot.com	8
http://www.cnti.info	6
http://translate.googleusercontent.com	4
http://webcache.googleusercontent.com	4
http://chemclass4spm.blogspot.com.au	3
http://chemclass4spm.blogspot.in	3
http://macphersonsec.mycybersphere.net	3
http://cc.bingj.com	2
http://chemclass4spm.blogspot.co.uk	2
http://chemclass4spm.blogspot.com.br	1
http://chemclass4spm.blogspot.com.ar	1
http://chemclass4spm.blogspot.co.nz	1
http://www.sirazlee.blogspot.com	1
http://www.yahoo.com	1
http://27.123.194.35	1
http://search.yahoo.com	1
https://northampton.blackboard.com	1
http://www.google.com.my	1
http://blendedschools.blackboard.com	1
http://chemclass4spm.blogspot.se	1

Acids and Bases

by Sadman Ridoy on Apr 30, 2009

Accessibility

Categories

Tags

Upload Details

Usage Rights

25 Embeds 11,263

Statistics

Acids and Bases — Webinar Transcript