ACIDS BASES and ALKALI AND SALT PREPARATION
The substance which have pH less than 7.
Strong Acids
- They completely dissociated in water to release H+ ions
- Hydrochloric Acid HCl
- Sulphuric Acid H2SO4
- Nitric Acid HNO3
- Phosphoric Acid H3PO4
- HCl H+ + Cl–
- pH = 1-3
Weak Acids
- They are partially dissociated in water to release H+ ions
- Vinegar: Ethanoic Acid
- Lemon: Citric Acid
- CH3COOH CH3COO– + H+
- pH = 5-7
The substance which have pH greater than 7.
- Metal Oxides, Metal Hydroxides, Metal Carbonates
- Lithium Oxide, Lithium Carbonate, Lithium Hydroxide
- Alkali are the soluble bases. So bases that can dissolve in water.
- Alkali metal hydoxide
- They release hydroxide ions when dissolved in water.
Acids Alkali and Titration
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INDICATORS
| Acids | Bases |
| Taste Sour | Taste Bitter |
| Not soapy | Feels soapy |
| have pungent small | do not have a pungent smell |
| When ionize give hydrogen ions | Give hydroxide ions |
| Turns blue litmus red | Turns red litmus Blue |
| eg Hydrochloric Acid | eg Sodium Hydroxide |
| Sulphuric Acid |
NEUTRALIZATION REACTION
Acid + Base Salt + Water
Metal Acid
Hydrochloric Acid -makes chloride salt
Sulphuric Acid – makes sulphate salt
Nitric Acid – makes nitrate salt
Eg
Sodium Chloride + Water Sodium Hydroxide + Hydrochloric Acid
NaOH + HCl NaCl + H2O
Potassium Oxide + Sulphuric Acid Potassium Sulphate + Water
K2O + H2SO4 K2SO4 + H2O
Magnesium Hydroxide + Nitric Acid Magnesium Nitrate + Water
Mg(OH)2 +2HNO3 Mg(NO3)2 +2H2O
Calcium Carbonate + Sulphuric Acid Calcium Sulphate + Carbonate + Water
CaCO3 + H2SO4 CaSO4 + H2O + CO2
REACTIONS OF ACIDS
- Metal + Acid = Salt + Hydrogen
- Metal Oxide + Acid = Salt + Water
- Metal Hydroxide + Acid = Salt + Water
- Metal Carbonate + Acid = Salt Water + CO2
2Na + 2HCl 2NaCl +H2
Making Insoluble salts
Mix two soluble acids and Bases
The salt will come out as a precipitate
The precipitate is then filtered and dried.
The filter paper will contain an insoluble salt.
To determine the exact volume of acid and base required to make the salt, titration is carried out.
Making Soluble Salts
Mix the insoluble base into the aqueous solution of the acids.
Dissolve the base into the acid until no base can be dissolved.
Filter the solution to remove excess undissolved base.
The run off is then crystallized to remove all the water.
After evaporation the crystals will collect at the size of the vessel.
The crystals can then be dried.
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References:
BBC Bitesize
Wikipedia
Wikimedia Commons