EL - Making salts

Question 1

What type of compounds are salts?

Answer 1

Ionic compound.

Question 2

What is the pH of acids?

Answer 2

Less than 7.

Question 3

What is the pH of bases?

Answer 3

More than 7.

Question 4

In what type of reaction do acids react with bases to form a salt and water?

Answer 4

Neutralisation reaction.

Question 5

What happens in a neutralisation reaction?

Answer 5

Acids react with bases to form a salt and water.

Question 6

What are salts formed from and what does this mean?

Answer 6

Positively charged cations and negatively charged anions meaning their product is neutral.

Question 7

Why are salts neutral?

Answer 7

Because they are formed from positively charged cations and negatively charged anions meaning their product is neutral.

Question 8

When naming salts, which bit do you put first - the cation of the anion?

Answer 8

Cation bit first and then the anion.

Question 9

Are salts soluble in water?

Answer 9

Can be soluble or insoluble in water.

Question 10

Are lithium, sodium, potassium and ammonium salts soluble or insoluble in water?

Answer 10

Soluble.

Question 11

Are nitrates soluble or insoluble in water?

Answer 11

Soluble.

Question 12

Are most chlorides, bromides and iodides soluble or insoluble in water?

Answer 12

Soluble.

Question 13

What are exceptions to the fact that most chlorides, bromides and iodides are soluble in water?

Answer 13

Silver halides, copper iodide (forms a white precipitate), lead chloride and lead bromide (white precipitates) and lead iodide (yellow precipitate).

Question 14

Are silver halides, copper iodide, lead chloride and bromide and lead iodide soluble or insoluble in water?

Answer 14

Insoluble.

Question 15

Are most sulfates soluble or insoluble in water?

Answer 15

Soluble.

Question 16

What are exceptions to the fact that most sulfates are soluble in water?

Answer 16

Barium sulfate, calcium sulfate and lead sulfate, which all form white precipitates.

Question 17

Are most hydroxides soluble or insoluble in water?

Answer 17

Insoluble.

Question 18

What are exceptions to the fact that most hydroxides are insoluble in water?

Answer 18

Lithium, sodium, potassium, strontium, calcium, barium and ammonium hydroxides.

Question 19

Are most carbonates soluble or insoluble in water?

Answer 19

Insoluble.

Question 20

What are exceptions to the fact that most carbonates are insoluble in water?

Answer 20

Lithium, sodium, potassium and ammonium carbonates.

Question 21

What colours do the insoluble carbonates form?

Answer 21

Copper carbonate - blue-green.
Silver carbonate - yellow.
Most other carbonates - white.
Iron(II) - off-white.

Question 22

What colour precipitate does insoluble copper carbonate form?

Answer 22

Blue-green.

Question 23

What colour precipitate does insoluble silver carbonate form?

Answer 23

Yellow.

Question 24

What colour precipitate do most insoluble carbonates form?

Answer 24

White.

Question 25

What colour precipitate does iron(II) carbonate form?

Answer 25

Off-white.

Question 26

What reaction can you use if the salt you want to make is insoluble?

Answer 26

Precipitation reaction.

Question 27

When you use a precipitation reaction, what salt would you be wanting to form?

Answer 27

An insoluble salt.

Question 28

In what state/conditions do precipitation reactions occur?

Answer 28

Aqueous solutions.

Question 29

When do precipitation reactions occur?

Answer 29

In aqueous solutions, when cations and anions combine to form and insoluble ionic salt called a precipitate.

Question 30

What do you need to do a precipitation reaction?

Answer 30

Two solutions that contain the ions you need to make the salt.

Question 31

What solutions would you do a precipitation reaction with to make lead chloride and why?

Answer 31

Lead nitrate solution (nitrates are insoluble) and sodium chloride solution (most chlorides are soluble).

Question 32

How do you carry out a precipitation reaction?

Answer 32

Pick two solutions that contain the ions you need to make the salt and mix them.

Once the salt has precipitated out (and is lying at the bottom of your flask), filter it from the solution, wash it and then dry it on filter paper.

Question 33

How do you make a soluble salt using a metal or an insoluble base?

Answer 33

Pick the right acid, plus a suitable metal or an insoluble base (a metal oxide or hydroxide).

Add the solid metal, metal oxide or hydroxide to the acid - it will dissolve in the acid as it reacts. It has all been neutralised when no more solid dissolves and it sinks to the bottom of the flask.

Filter out the excess metal, metal oxide or hydroxide to get the salt solution.

To get pure, solid crystals of the salt, evaporate some of the water ( to make the solution more concentrated) and then leave the rest to evaporate very slowly. This is called crystallisation.

Question 34

How do you pick the right acid to mix with the metal/metal oxide/metal hydroxide when making soluble salts?

Answer 34

To make chlorides - hydrochloric acid
To make sulfates - sulfuric acid
To make nitrates - use nitric acid

Question 35

What acid do you use to make chlorides?

Answer 35

HCL

Question 36

What acid do you use to make sulfates?

Answer 36

Sulfuric acid

Question 37

What acid do you use to make nitrates?

Answer 37

Nitric acid

Question 38

How do you make soluble salts using an alkali?

Answer 38

You have to add exactly the right amount of alkali to just neutralise the acid - using a titration for example, with an indicator to show you exactly how much alkali neutralises a known volume of acid.

Once you have found out how much alkali you need to neutralise the acid, repeat the titration by combining these volumes again, without adding indicator as this will contaminate the salt.

Then just evaporate off the water to crystallise the salt as normal.

Question 39

What method/technique can you use to make soluble salts using an alkali?

Answer 39

A titration.