Chemistry Remove Summer Exam

Metal Extraction Method Table

What is an ore?

A rock/mineral containing enough metal compounds to make it economical to extract.

What is electrolysis?

Extraction of a metal ore using electricity.

What is extracting by using carbon called?

Smelting

What is an electrolyte?

A compound capable of conducting electricity when melted (ionic substance)

Electrolysis of aluminium oxide

1. Extract your ore (bauxite) - impure Al₂O₃

2. Purify the ore to give pure Al₂O₃

3. Melt the Al₂O₃ to form an electrolyte

4. Pass electrcity through the liquid Al₂O₃

What happens next in the electrolysis of aluminium oxide?

Anode (+) attracts anions (-) (oxide ions).

2O^2- → O₂ + 4e^-

Cathode (-) attracts cations (+) (aluminium ions)

Al³⁺+3e^- → Al

Aluminium ions are reduced by electrons to form aluminium metal

What is corrosion?

The oxidation of metals.

What is iron said to do instead of corrode?

Rust

What reaction is rusting?

An oxidation reaction.

Iron becomes hydrated iron^(III) Oxide.

Rust redox reaction:

4Fe + 3O₂ → 2FeO₃

The arrow is water

What is needed for rusting?

Iron, water and oxygen

What is a good catalyst for rusting?

Sodium chloride

Barrier Methods of preventing rusting

Barrier Methods prevent water and oxygen from reaching the iron:

• Painting

• Oil

• Grease

• Plastic Coating

Sacrificial methods of preventing rusting:

Sacrificial Methods involve allowing a more reactive metal to corrode instead of the iron:

• Galvanising - Coating iron with Zn

• Sacrificial Protection - Zn/Mg

Zinc acts as both a…

sacrificial method and a barrier method

Why will iron not rust even if the zinc coating is broken?

The electrons produced by zinc are given to the iron which reduces back to normal iron (stops rusting).

Uses of aluminium:

aircraft, drinks cans, electrical power lines

Uses of copper:

wires, pans, water pipes

Uses of iron:

converted to steel (mostly turned into alloys)

Uses of steel:

building and cutlery

What is group 7 called?

The halogens

The halogens are…

A group of reactive, non-metallic elements which are all diatomic molecules.

Colours and physical states of chlorine, bromine and iodine at room temperature:

The melting points and boiling points _______ as you go down the group.

increase

Why do the melting and boiling points increase as you go down the group?

This is due to increasing molecular forces as the atoms become larger, so more energy is required to overcome these forces.

Fluorine (F₂) colour,state and reactivity:

A pale yellow gas - highly reactive

Astatine (At₂) colour,state and reactivity:

A black solid - very unreactive

The reactivity _______ as you go down the group.

decreases

Explain the reactivity in group 7 in terms of electronic configuration:

• All group 7 elements can gain one electron to obtain a full outer shell.

• The easier it is for a halogen to attract an electron, the more reactive the halogen will be.

• As you go down group 7, the extra electron becomes further away from the nucleus which makes it harder to attract.

• This causes them to get less reactive as you go down the group.

Describe a test for chlorine:

It bleaches damp litmus paper white.

A more reactive halogen will displace a…

less reactive halogen.

What is a redox reaction?

Reduction/oxidation (gain or loss of oxygen)

However, it can sometimes refer to reactions involving the movement of electrons.

OIL RIG

Oxidation Is Loss of electrons.

Reduction Is Gain of electrons.

What is a halogen called when it becomes an ion?

A halide ion (Halogen^-)

Halogens Reactivity: Most Reactive to least reactive

Chlorine

Bromine

Iodine

Halogens In Solution Results

Halogen Displacement Reactions Results

What is a covalent bond?

A shared pair of electrons between two neighbouring nuclei.

Are covalent bonds strong?

Yes

Covalent Bond Dot and Cross Diagram

What is the structure of covalent bonds called?

Simple molecular

Simple molecular structures have…

LOW melting and boiling points.

Weak intermolecular forces.

Why do they have low melting and boiling points?

There are only weak intermolecular forces which do not need much energy to overcome.

Allotropes of carbon

Diamond, Graphite and C₆₀ Fullerene

Which of these have giant covalent structures?

Diamond and graphite

Giant covalent structures have…

High melting points.

Why do Giant Covalent Structures have high melting points?

Because lots of energy is requires to break the many strong covalent bonds.

Do covalent compounds usually conduct elctricity?

No, as they have no delocalised electrons.

Graphite is an exception.

Structure of Diamond

Giant Lattice

Diamond is very hard because:

Each carbon atom is contently bonded to four other carbon atoms.

The Covalent bonds are very strong.

Diamond does not conduct electricity because…

Each atom is using all of its electrons to form four covalent bonds, so there are no delocalised electrons.

Graphite is…

Soft and slippery.

What is the structure of graphite?

Giant Lattice

Graphite forms in layers that are free to slide over each other because there are only weak forces between the layers.

Graphite can…

Conduct electricity and heat.

Graphite can conduct electricity and heat because…

Each carbon atom only forms three bonds. This leaves some delocalised electrons which are free to move and carry charge.

C₆₀ Fullerne Structure

Simple molecular structure.

C₆₀ Fullerne has…

A low melting and boiling point because there are only weak intermolecular forces which require little energy to overcome.

C₆₀ Fullerene is also…

Soft and slippery

Use of C₆₀ Fullerne:

Drug delivery due to its hollow structure.

Graphite information

• Giant Lattice Structure (layers)

• 3 covalent bonds formed by each carbon atom plus 1 weak attraction between the layers of carbon atoms

• Soft, shiny, grey

• Conducts electricity

• High melting and boiling point

Diamond Information:

• Giant Lattice Structure

• 4 covalent bonds per carbon atom

• Very high boiling and melting point

• Hard, transparent

• Can not conduct electricity (no delocalised electrons)

• Each carbon atom bonds in a tetrahedral shape

C₆₀ Fullerene Information:

• Simple molecular structure

• Each carbon atom is bonded to 3 others

• High melting and boiling point

• Bonds between molecules are weak

• Can not conduct electricity (no delocalised electrons)

Silicon Dioxide

• Silicon forms 4 covalent bonds and oxygen forms 2 covalent bonds

• Giant Structure

• High melting and boiling point

• Can not conduct electricity (no delocalised electrons)

Atoms which lose electrons become

Positive Ions (Cations)

Atoms which gain electrons become

Negative Ions (Anions)

Pb
Cu
Fe
Ag
Zn

2+
2+
2/3+
+
2+

Ionic bonding is the

Strong electrostatic attraction between two oppositely charged ions.

Ions compounds have a

Giant Ionic Lattice Structure

Dot and Cross Diagram

Why do ionic compounds have high melting and boiling points?

This is due to their strong electrostatic forces of attraction, which take a lot of energy to overcome.

Ionic compounds can not

Conduct electricity as solids because the ions are fixed and not free to move around.

Ionic compounds can

Conduct electricity when molten (melted) or dissolved in water because the ions are free to move around.

Test for Hydrogen

Hold a burning splint to mouth of test tube containing gas. Listen for squeaky pop.

Test for Oxygen

Relights a glowing splint

Test for Carbon Dioxide

Bubble through lime water (Calcium Hydroxide). Turns cloudy.

Test for Ammonia - ONLY ALKALI GAS

Turns Damp RED litmus BLUE.

Test for Chlorine

Bleaches damp litmus paper.

Test for Water

Boils at exactly 100 degrees.

What Flame is needed for a flame test?

A roaring blue flame as safety flame already has a colour.

Result for these Cations:
L²+
Na+
K+
Ca²+
Cu²+

Red
Yellow
Lilac
Orange/Red
Blue/Green

NH⁴+ Test

Add sodium hydroxide solution and warm. Turns damp red litmus paper blue.

Test for
Cu²+
Fe²+
Fe³+

Add sodium hydroxide.
Colour of metal hydroxide precipitate formed:
Blue
Green
Brown

Test for
Cl-
Br-
I-

Add dilute nitric acid and silver nitrate solution.
Colour of silver halide precipitate:
White
Cream
Yellow

Test for SO4²-

Add dilute hydrochloric acid and barium chloride solution:
White barium sulphate precipitate formed.

Test for CO3²-

Add dilute hydrochloric acid:
Bubble the gas given off through limewater. It should turn cloudy.

Acid is used to

destroy CO3²- ions

Why are alkali metals stored under oil?

Because they react very vigorously with oxygen and water, including moisture in the air

General equation for the reaction of Alkali Metals with oxygen

Metal + Oxygen --> Metal oxide

What is the balanced equation for the reaction of sodium with oxygen? (Include state symbols)

4Na(s) + O2(g) --> 2Na2O(s)

General equation for the reaction of alkali metals with water

Metal + Water --> Metal hydroxide + Hydrogen

What is the balanced equation for the reaction of potassium with water? (Include state symbols)

2K(s) + 2H20(l) --> 2KOH(aq) + H2(g)

Why do all the Alkali Metals react in a similar way with water?

They all have 1 electron in their outer shell

What would you observe when lithium metal reacts with water containing universal indicator solution? (4 points)

Lithium moves slowly on the surface of the water
Fizzing
The metal gets smaller and eventually disappears
Universal indicator turns purple

What would you observe when sodium metal reacts with water containing universal indicator solution? (5 points)

Sodium moves quickly on the surface of the water
Fizzing
Sodium melts to form a ball
The metal gets smaller and eventually disappears
Universal indicator turns purple

What would you observe when potassium metal reacts with water containing universal indicator solution? (6 points)

Potassium moves very quickly on the surface
Fizzing
Potassium melts to form a ball
A lilac flame
The metal gets smaller and eventually disappears
Universal indicator turns purple

Why does the universal indicator turn purple?

An alkaline solution of the metal hydroxide is formed

Which ion causes the solution to become alkaline?

The hydroxide ion (OH-)

What is the trend in reactivity down Group 1

Reactivity increases as you go down the group

Why does reactivity increase down Group 1?

Down the group, the number of electron shells increases.
The outer electron is therefore further away from the nucleus and is lost more easily. There is more shielding as you go further down the group.