Metals reacting with oxygen

Most metals will react with oxygen. During this reaction the following is formed:

Metal + oxygen —> Metal oxide

Magnesium + oxygen —> magnesium oxide

2Mg + O2 —> 2MgO

This is referred to as an OXIDATION reaction. The metal has GAINED oxygen.

Mid and low reactive metals are found as ORES. An ore is a naturally occurring material from which a metal or mineral can be extract-ed.

For mid and low reactivity metal oxides can be REDUCED to the metal by heating with carbon.

Displacement Reactions

Displacement is when a more reactive metal takes the place of a less reactive metal in a solution.

How do we know a displacement reaction has taken place?

•Colour change (black à blue)

•Heat given out (exothermic reaction)

•New product is formed (a metal salt)

Knowledge quiz 1

1.Why do metals increase in mass when they burn?

2.In terms of oxygen what is reduction?

3.What is an ore?

4.Why can carbon be used to reduce copper oxide?

5.When one chemical in a reaction is reduced, the other is oxidized. What sort of reaction is this?

Knowledge quiz 2

1.What is a displacement reaction?

2.In terms of electrons what is oxidation?

3.In terms of electrons what is reduction?

4.Why wont gold displace copper?

5.Name a metal that is more easily oxidised than sodium

Knowledge quiz 3

1.What is the symbol for an electron?

2.Use electrons to complete this ionic equation : Ca —> Ca2+

3.Which process is needed to extract iron from iron ore?

4.Which process is needed to extract aluminium from aluminium ore?

5.Which element is commonly heated with copper oxide in order to reduce the metal?

Knowledge quiz 4

1.What ions do acids and alkalis produce?

2.Write an ionic equation for neutralisation

3.Finish the general equation for: acid + alkali —>

4.Write the general equation for: acid + metal —>

5.Write the general equation for: acid + carbonate —>

Knowledge quiz 5

1.Name the salt that will be made when magnesium neu-tralises sulphuric acid

2.Name the salt that will be made when copper oxide neutralises nitric acid

3.Name the salt that will be made when copper neutral-ises hydrochloric acid

4.How is a strong acid different to a weak one?

5.How is a dilute acid different to a concentrated one?

Knowledge quiz 6

1.What is an electrolyte made of?

2.Why can electrolytes conduct electricity?

3.Name the electrode + ions are attracted to

4.Name the electrode – ions are attracted to

5.What happens to – ions when they reach the elec-trode?

Reactivity series

Knowledge quiz 7

1.Why can’t solid ionic compounds conduct?

2.Why is electrolysis expensive

3.When extracting aluminium why is the ore dis-solved in cryolite?

4.When extracting aluminium what gas is made at the anode

5.Why are the carbon anodes replaced so often?

Positive

Anode

Negative

Is

Cathode

Electrolytes contain free ions. This is why they can conduct elec-tricity.

Required Practical Finding the reacting volumes of solutions of acids and alkalis by titration

-A number of different skills are needed to carry out a titration with accuracy. -The volumes of the solutions used are either measured as a fixed volume or a variable volume. The point of neutralisation is determined by an indicator. -For acid/alkali titration the indicator used is PHENOLPHTHALEIN or METHYL ORANGE – this is made from one compound.

Higher!! Strong and weak acids

These have the SAME concentration but different pH values (strength). This is because

CONCENTRATION – the amount of a chemical dissolved in a cer-tain volume of a solution. STRENGTH – is the amount of hydrogen ions which have ionised completely in the water. In hydrochloric acid ALL the hydrogen ions

(H+ ) have fully ionised:

HCl (aq) —> H+ (aq) + Cl – (aq)

Whereas, in ethanoic acid the hydrogen ions are only partially ion-ised, leaving a high percentage of unreacting molecules in the so-lution.

CH3COOH (aq) —> CH3COO- (aq) + H+ (aq)

pH scale

pH is a number to show the acidity or alkalinity of a solution based on a scale on which 7 is neutral, lower are acid and higher values more alkaline. The indicator colours are produced when UNIVERSAL INDI-CATOR is added to a solution. Acids produce hydrogen ions H+ and alkalis produce hydrox-ide ions OH- when dissolved in water.

In all neutralisation reactions the equation is:

H+ (aq) + OH-

(aq) —> H2O (l)

The acid used provides the metal salt produced with its name: Hydrochloric acid —> chloride

Sulfuric acid —> sulfate

Nitric acid —> nitrate

Redox reactions in terms of electrons. Higher:

Method 1. Use the pipette and pipette filler to add 25 cm3 of alkali to a clean conical flask. 2. Add a few drops of indicator and put the conical flask on a white tile (so you can see the colour

of the indicator more easily). 3. Fill the burette with acid and note the starting volume. 4. Slowly add the acid from the burette to the alkali in the conical flask, swirling to mix. 5. Stop adding the acid when the end-point is reached (the appropriate colour change in the

indicator happens). Note the final volume reading. 6. Repeat steps 1 to 5 until you get consistent readings 7. It is important to repeat the titration several times to check that your titre value is consistent so

that your calculations are reliable. 8. If universal indicator is used, the colour changes gradually through a range of colours. On the

other hand, a single indicator like litmus or phenolphthalein gives a sharp end-point where the colour changes suddenly.

Chemistry knowledge organiser Unit 4 chemical change