Preparing pure salts and solubility

How are pure, dry hydrated copper sulfate crystals prepared from copper oxide?

React copper oxide with sulfuric acid, filter, evaporate and crystallise.

Why is copper oxide added in excess?

To ensure all sulfuric acid reacts.

Why is excess copper oxide filtered off?

To remove unreacted solid.

Why is a water bath used when preparing copper sulfate crystals?

To gently evaporate water without overheating the crystals.

What equipment is used for acid-alkali titration?

Burette, pipette and a suitable indicator.

What is the purpose of a pipette in titration?

To measure a fixed, accurate volume of solution.

What is the purpose of a burette?

To deliver and measure an accurate variable volume of solution.

Why is an indicator used in titration?

To show when neutralisation is complete.

How are pure, dry crystals obtained after titration?

Evaporate some water, cool to crystallise, then filter and dry.

Which sodium salts are soluble?

All common sodium salts.

Which potassium salts are soluble?

All common potassium salts.

Which ammonium salts are soluble?

All common ammonium salts.

Are all nitrates soluble?

Yes, all common nitrates are soluble.

Which common chlorides are insoluble?

Silver chloride and lead chloride.

Which common sulfates are insoluble?

Lead, barium and calcium sulfates.

Which common carbonates are insoluble?

Most, except sodium, potassium and ammonium carbonates.

Which common hydroxides are insoluble?

Most, except sodium, potassium and ammonium hydroxides.

What is a precipitate?

An insoluble solid formed when two solutions react.

How can you predict whether a precipitate forms?

Use solubility rules to identify any insoluble product.

How do you prepare an insoluble salt?

Mix suitable soluble solutions, filter the precipitate, wash and dry it.

What is the purpose of washing a precipitate?

To remove soluble impurities.

Why is the precipitate dried?

To remove remaining water and obtain a dry salt.