S3 Salts

Question 1

What are the use of salts around us?(3)

Answer 1

Table salt, fertilisers, photography

Question 2

Are all nitrates soluble?

Answer 2

Yes

Question 3

Are all halides (grp VII) soluble?

Answer 3

Yes except lead and silver halides

Question 4

Are all sodium, potassium and ammonium salts soluble?

Answer 4

Yes

Question 5

Are all carbonates soluble?

Answer 5

No except sodium, potassium and ammonium carbonates.

Question 6

Are all sulfates soluble?

Answer 6

Yes except Lead(II), calcium and barium(II) (lazy charlie brown)

Question 7

Are all hydroxides soluble?

Answer 7

No except hydroxides of group I elements, ammonium and sparing calcium

Question 8

Are all oxides soluble?

Answer 8

No except oxides of ammonium and group I elements

Question 9

How do you prepare soluble salts by reacting with acids?

Answer 9

Reaction with acids and excess reactive metals, base and carbonate.

Question 10

Why do you use excess reactive metal/base/carbonate when preparing soluble salts?

Answer 10

The acid will all be reacted due to the excess solid reactant used, and the excess solid reactant can easily be filtered out.

Question 11

What is the general state equation for reactions with acids?

Answer 11

Aq + s = aq

Question 12

When is titration needed with soluble salts?

Answer 12

If both starting reactants are soluble

Question 13

Why is titration least preferred?

Answer 13

Titration is tedious because exact amount of reactants have to be added.

Question 14

How to prepare insoluble salts with precipitation?

Answer 14

Select 2 soluble reactants that will react to form the salt. Since the salt is insoluble, it can easily be precipitated as a solid and purified by filtering and washing with distilled water.

Question 15

What is the general state equation for precipitation?

Answer 15

aq+aq=s

Question 16

Name the process of precipitation.

Answer 16

1) pour solution 1 to solution 2 to allow precipitation to take place.
2) filter the solution to obtain the insoluble salt as residue.
3) wash salt with distilled water to remove impurities.
4) dry the salt using filter paper.

Question 17

What are anhydrous salts?

Answer 17

They do not exist as liquid state while hydrated salts do.

Question 18

How to prepare soluble salts with excess reactive metal/base/carbonate?

Answer 18

Add excess reactive metal/base/carbonate to hot dilute acid and stir consistently until nothing else can dissolve. Remove the excess base by filtration. Heat the filtrate to evaporate most of the water and produce a saturated solution. Dip a clean dry glass rod in the solution to test for saturation. Allow the saturated solution to cool and crystals will be formed upon cooling. Filter the zinc sulfate crystals and wash with deionzed water. Dry them using filter paper.

Question 19

How to prepare soluble salts with titration?

Answer 19

Pipette a fixed amount of acid into a clean conical flask. Add a few drops of an indicator, then fill a burette with the reactant. Add it few drops at a time, into the conical flask until the indicator changes color. Record the volume of reactant used, then repeat the experiment with the same volume of acid and reactant in a clean conical flask without any indicator. The solution is then placed in an evaporating dish and crystals of sodium sulfate are obtained by crystallisation.

Question 20

What are the 6 reactive metals that can be used for acid reaction to form salt?

Answer 20

1) mg
2) Al
3) Zn
4) Fe
5) Sn
6) Pb