Unit 1

Question 1

Define activation energy ?

Answer 1

The amount of energy required to start the reaction

Question 2

What happens when temperature is increased.

Answer 2

At higher temperatures more particles have energy equal to or above the activation energy and so therefore there is more successful collisions

Question 3

Enthalpy means

Enthalpy change means

Answer 3

Energy

Energy change

Symbol is (H)

Question 4

What can catalysts be used for

Answer 4

They can lower the activation energy

Make the process more economical

Question 5

The enthalpy change is ?

Answer 5

The enthalpy change is the start to end value difference

Question 6

Define activated complex

Answer 6

The maximum energy point along the reaction path

Question 7

On the graphs the shaded area represents all the molecules with energy greater than the activation energy. An increase in activation energy would cause a decrease in the shaded area

Answer 7

.

Question 8

How can covalent bond length be measured?

Covalent radius is ?

Answer 8

X-ray diffraction

The centre to the edge of the molecule. Not the bond length

Question 9

Atomic size . Explain

Answer 9

Decreases across the periodic table - protons added moving across so there is a greater nuclear charge, with the same amount of shielding.

Increases down. - new electron shell added each time moves down
- greater shielding from the extra layer of electrons

Question 10

What is an ion?

Answer 10

An ion is an atom which has lost or gained an electron

Question 11

Define ionisation energy ?

Answer 11

Ionisation energy is the energy required to completely remove 1 mole of electrons from one mole of atoms in the gaseous state

Question 12

When subbing in from data booklet make sure use state symbols

Answer 12

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Question 13

Ionisation energy . Explain periodic table of This!

Answer 13

Decreases down:
- more electron shells and more shielding

• decreased attraction between outer electrons and nucleus, less energy required to move electron

Increases along:
- more protons added going across, so greater nuclear charge

• greater attraction between nucleus and outer electron being removed, so more energy required

Question 14

Define electro negativity !

Answer 14

A measure of the attraction an atom ya for its bonding electrons

Question 15

High electronnegativity :

Low electro negativity :

Answer 15

High - attracts electrons strongly

Low - attracts electrons weakly

Question 16

Electro negativity on the periodic table. Explain.

Answer 16

Decreases down

• more electron shells being added and more shielding
• decreases attraction between outer electron and nucleus, so lower electro negativity

Increases
- more protons being added across so greater nuclear charge

• greater attraction between nucleus and outer electron being removed so more energy required

Question 17

Group 0

Quick facts

Answer 17

• monatomic
• covalent bonds
• IMFs

Examples : helium and argon

Question 18

Cov network

Answer 18

Carbon, silicon, boron

Question 19

Fullerene is ?

Answer 19

A form of carbon which has a covalent molecular structure

Question 20

Group 7

Quick facts

Answer 20

• bonding: covalent
• structure : molecular
• they are diatomic elements

Examples: fluorine, chlorine

Question 21

Non polar covalent bonds are formed when?

Polar covalent bonds are formed when?

Answer 21

When the electronegativity values of each atom are the same (>0.4)

Formed when the electronegativity values of each atom are different

Question 22

A difference in electronegativity causes a ?

Answer 22

Permanent dipole

And the more electronegative of the two molecules has the dots on the line nearest it and has a delta negative sign beside it

Question 23

Polar shape is ?

Non polar shape is

Answer 23

Asymetrical

Symmetrical

Question 24

More electrons means the higher the LDF is

Answer 24

.

Question 25

How are permanent dipoles formed?

Answer 25

Occur when electrons are unequally shared (electronegativity difference)

Question 26

When does hydrogen bonding occur ?

Answer 26

When H is directly bonded to N, O, F Must have line in between to be a hydrogen bond

Question 27

Facts - H2O, HF,NH3. All have higher boiling points due to the presence of hydrogen bonds between the molecules which means that more energy is required to overcome these intermolecular forces

Answer 27

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Question 28

Why does ice float?

Answer 28

When water molecules form ice they create a large structure with large spaces between the molecules which results in it being less dense than water and so the ice floats

Question 29

Reasons why an element has a higher boiling point than another ? (Memorise word for word this)

Answer 29

The more electrons there are means the stronger the London dispersion force is. This makes it harder to break up the bonds, the further down the halogens, as the number of electrons increase. Example : Sulfur has a higher number of electrons than phosphorus meaning the London dispersion force is higher, making it harder to break intermolecular bonds. S8 has more electrons than P4, and so it has a higher London dispersion force

Question 30

The more intermolecular forces, the more viscous a substance is (thicker)

Answer 30

Viscous means how thick it is Example : syrup

Question 31

Water is more viscous than ethanol because ?

Answer 31

Water CAN form hydrogen more hydrogens bonds

Question 32

How to know what dissolves what ?

Answer 32

Polar dissolves polar Non polar dissolves non polar ‘Like dissolves like’

Question 33

Miscibility ? Define miscible liquids Define immiscible liquids

Answer 33

Miscible liquids is a liquid that can mix Immiscible liquids can’t mix (I.e. oil and water)

Question 34

The best group for being an oxidising agent is? The best group for being a reducing agent is?

Answer 34

group 7 (halogens). Because they are very electronegative and also have a greater attraction for bonding electrons Group 1 because they want to gain a full outer shell (metals)

Question 35

Oxidising agents accept electrons Reducing agents give electrons

Answer 35

.

Question 36

Balancing equations steps:?

Answer 36

- balance everything except oxygen and hydrogen - balance Oxygen by adding H2O - balance H by adding H+ - add electrons to same side as hydrogens to make charges equal on both sides

Question 37

How are London dispersion forces formed/caused?

Answer 37

They are caused by the movement of electrons, as electrons move round the nucleus, one side of the atom becomes positive, and the other becomes negative for a fraction of a second. This causes a temporary dipole, this then causes a neighbouring atom to form an induced dipole for a fraction of a second

Question 38

Are ionic lattices polar or non polar ?

Answer 38

Polar