Edexcel IGCSE Chemistry Acids,Alkali And Titration

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

AcidsBases
Taste SourTaste Bitter
Not soapyFeels soapy
have pungent smalldo not have a pungent smell
When ionize give hydrogen ionsGive hydroxide ions
Turns blue litmus redTurns red litmus Blue
eg Hydrochloric Acideg 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:

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