Salts

How do you decide which method to use for salt preparation?

First check if the salt is soluble or insoluble.

What method is used if the salt is insoluble?

• Precipitation method (mix two soluble solutions to form an insoluble precipitate).

  1 Mix two soluble solutions

  2	Filter off the precipitate

  3	Wash precipitate with cold distilled water

  4	Dry the precipitate in a warm place

If the salt is soluble, what is the next step to decide method?

Check if the base is soluble (alkali) or insoluble (metal, oxide, carbonate).

When is titration used for salt preparation?

When both reactants are soluble, usually acid + alkali (like NaOH, KOH, NH₄OH).

When is the excess solid method used for salt preparation?

When an insoluble solid (metal, oxide, or carbonate) reacts with an acid.

Which salts are prepared by titration?

Salts containing Group 1 metals (Na⁺, K⁺) or ammonium ion (NH₄⁺).

Which salts are prepared by excess solid method?

Salts containing metals like copper(II), magnesium, zinc (transition metals or Group 2).

What type of material is used in the titration method?

Soluble metal hydroxides (alkalis).

What type of material is used in the excess solid method?

Insoluble metals, metal oxides, or metal carbonates.

What happens after titration is completed?

Neutralize exactly, then evaporate water to crystallize the salt.

What happens after using the excess solid method?

Filter off excess solid, then evaporate water to crystallize the salt.

How is an insoluble salt like barium sulfate prepared?

By precipitation — mixing two soluble solutions like barium nitrate and sodium sulfate.

How is copper(II) sulfate prepared?

By reacting excess copper(II) oxide with dilute sulfuric acid and crystallizing the solution.

How is sodium nitrate prepared?

By titration of sodium hydroxide with nitric acid, then evaporating the solution.

How is magnesium chloride prepared?

By reacting excess magnesium oxide with dilute hydrochloric acid and crystallizing the solution.

In the precipitation method, why must both starting materials be soluble?

So they can mix in solution to form an insoluble precipitate.

What is the key difference between titration and excess solid method?

Titration uses two soluble reactants; excess solid uses an insoluble solid and an acid.

Outline How Titration Works:

Step No.	Step
1	Add acid into a burette.
2	Use a pipette to measure alkali into a conical flask.
3	Add a few drops of indicator (methyl orange or phenolphthalein).
4	Slowly add acid from the burette into the alkali while swirling.
5	Stop when the indicator shows neutralization (colour change).
6	Record the volume of acid used.
7	Repeat titration for concordant results (within 0.10 cm³).
8	Repeat titration without indicator using the correct volumes.
9	Gently evaporate the pure solution to concentrate it.
10	Allow the concentrated solution to cool slowly.
11	Filter and dry the crystals between absorbent paper or in a warm place.

Outline how the Excess Method Works.

Step No.	Step
1	Warm the dilute acid gently (do not boil).
2	Add insoluble solid (metal, metal oxide, carbonate) to the acid while stirring.
3	Continue adding solid until no more reacts (solid remains unreacted).
4	Filter the mixture to remove excess unreacted solid.
5	Collect the filtrate (this is your salt solution).
6	Gently evaporate the filtrate to concentrate the solution.
7	Allow the concentrated solution to cool slowly.
8	Filter and dry the crystals between absorbent paper or in a warm place.