Chemisty || Acids C8

Question 1

Ph Scale?

Answer 1

Goes from 0-14,

Measure of how acidic or alkaline a solution is,

Neutral is 7 (green),

Acidic is 0-6 (red),

Alkali is 8-14 (blue and purple).

Question 2

How Does A Solution Get More Acidic?

Answer 2

The more hydrogen ions it has, the more acidic it is,

As hydrogen ions in a solution increase, the Ph decreases (because acids are 0-6).

Question 3

Acids For What In Water?

Answer 3

H+ ions.

Question 4

What Is A Base?

Answer 4

A substance that reacts with an acid to produce a salt and water.

Question 5

What Is An Alkali?

Answer 5

A base that is soluble in water,

Have a Ph of over 7,

Form OH- ions in water. These are called hydroxide ions.

Question 6

Alkalis Get More Concentrated When?

Answer 6

The OH- ions concentration increases.

Question 7

What Measures The Ph Of A Solution?

Answer 7

An indicator,

It’s a dye that changes colour depending on the Ph of a solution,

Examples of indicators include:

• Litmus,
• Methyl Orange,
• Phenolphthalein.

Question 8

Litmus?

Answer 8

Is red in acidic solutions,

Purple in neutral,

Blue in alkali.

Question 9

Phenolphthalein?

Answer 9

Is colourless in acidic solutions,

Colourless in neutral solutions too,

Pink in alkali.

Question 10

Methyl Orange?

Answer 10

Red in acidic,

Yellow in neutral,

Yellow in alkali too.

Question 11

Neutralisation?

Answer 11

The reaction between an acid and a base is called neutralisation,

This process produces a salt and water,

The concentration of hydrogen ions will be equal to the concentration of hydroxide ions.

Question 12

Practical?

Answer 12

Investigating neutralisation reaction between calcium oxide and dilute hydronic acid,

Measure dilute hydronic acid into a conical flask,

Measure fixed mass of calcium oxide using mass balance,

Add them together,

Wait for them to completely react and then record Ph,

Use a ph probe or a universal indicator to do this,

Repeat steps until all the acid has reacted. You’ll know all the acid has reacted when you Get I reacted calcium oxide sitting at the bottom of flask,

Plot graph showing ph changes.

Question 13

What Will Practical Graph Look Like?

Answer 13

When the base is first added, the ph changes slowly,

There is a sudden change in the ph as you approach neutral,

It is neutral when all the base has reacted with the acid.

Question 14

Ionise Means?

Answer 14

The acids split up to produce hydrogen ions (H+) and another ion,

This happens when the acid is in solution,

E.g. HCL —> H+ + Cl-.

Question 15

Strong Acids?

Answer 15

Ionise almost completely, meaning most of the acid molecules ionise and release H+ ions in water,

They tend to have lower Ph of around 0-2.

Question 16

Weak Acids?

Answer 16

Do not fully ionise in solution,

Only a small amount of the acid molecules ionise to release H+ ions,

Ph tends to be around 2-6.

Question 17

What Ionisations Are Equilibrium For Acids?

Answer 17

Weak acids are equilibrium, meaning they can ionise and then turn back to acid molecules,

Strong acids are not equilibrium and cannot turn back to molecules.

Question 18

Concentration Is?

Answer 18

How much acid there is in 1 litre (1 dm3) of water,

How watered down your acid is.

Question 19

Strength Of An Acid Is?

Answer 19

What proportion of the acid molecules ionise in water.

Question 20

Salts Are?

Answer 20

Ionic compounds.

Question 21

Hydraulic Acids Produce?

Answer 21

Chloride salts.

Question 22

Sulphuric Acids Produce?

Answer 22

Sulfate salts.

Question 23

Nitric Acids Produce?

Answer 23

Nitrite salts.

Question 24

Acid + Metal Oxide =?

Answer 24

Salt + Water.

Question 25

Acid + Metal Hydroxide =?

Answer 25

Salt + Water.

Question 26

Acid + Metal =?

Answer 26

Salt + Hydrogen.

Question 27

Test For Hydrogen?

Answer 27

Lighted splint and a squeaky pop.

Question 28

Acid + Metal Carbonate =?

Answer 28

Salt + Water + Carbon Dioxide.

Question 29

Test For Carbon Dioxide?

Answer 29

Limewater will turn milky.

Question 30

How To Make A Soluble Salt?

Answer 30

React an acid that contains an ion you want the salt to have and a insoluble base you want the salt to have,

E.g. copper oxide + sulphuric acid = copper sulphate,

Start by heating the acid in a water bath (this speeds the reaction up),

Do this in a fume cupboard to avoid releasing acid fumes,

Then add the base,

There should be some of the base leftover (this means it is in excess of base which is good because it means there’s not excess acid),

Filter the excess solid to get a solution containing only the salt and water,

Heat the solution to evaporate water,

Allow salt to crystallise.

Question 31

Making Insoluble Salts?

Answer 31

Process called Precipitation Reaction,

You pick two soluble salts and react them together to get an insoluble salt.

Question 32

Necessities For Making A Salt?

Answer 32

Reacting acid with a insoluble reactant such as:

• A metal,
• A metal oxide,
• A carbonate,

The reactant depends on what salt you are making,

For example: copper doesnt react with dilute acids so copper salts can’t be made this way,

Sodium is too reactive to be used safely to make salts.

Question 33

Salt Names Are Formed How?

Answer 33

First part comes from metal, second part comes from acid,

E.g. Copper + Hydrochloric Acid = Copper Chloride.

Question 34

Why Use Metal Oxides Instead Of Pure Metals When Making Salts?

Answer 34

Because the pure metals are flammable whilst carbonates are not.

Question 35

Soluble Salt Examples?

Answer 35

Sodium,

Potassium,

Ammonium,

Nitrates,

Chlorides (minus silver and lead chloride),

Sulfates (minus lead, barium and calcium).

Question 36

Insoluble Salt Examples?

Answer 36

Common carbonates and hydroxides,

(Minus sodium, potassium and ammonium).

Question 37

If Salt And Water Are The Products, What Are The Reactants?

Answer 37

Metal Oxide + Water

Question 38

Core Practical - Copper Sulphate Preparation?

Answer 38

Measure set amount of dilute sulphuric acid,

Place into a water bath of 50 degrees (we use a water bath and not a bunsen because we can control temperature),

Add copper oxide to acid,

Stir,

Add enough copper oxide to solution so there is an excess that lies at bottom of flask and won’t react,

Filter the excess out,

Place in dish and leave it to crystallise (over weekend on windowsill or by bunsen burner),

This allows crystallisation to occur and blue crystals (shards) will form called Copper Sulphate.

Question 39

Small Crystals Form When?

Answer 39

Something is heated quickly,

This can be done by a Bunsen burner.

Question 40

Large Crystals Form When?

Answer 40

The solution is heated slowly,

This can be done by placing the solution on a windowsill.

Question 41

How Do We Know A Chemical Reaction Has Took Place?

Answer 41

Because the solid (copper oxide) will dissolve into the acid.

Question 42

Why Is Excess Left?

Answer 42

So we know all the acid has reacted fully with the copper oxide.