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Question 1

What is a hydrocarbon?

Answer 1

A hydrocarbon is a compound only containing hydrogen and carbon.

Question 2

What are symmetrical alkenes?

Answer 2

Symmetrical alkenes have the same groups either side of the double bond.

Question 3

What is an electrophile?

Answer 3

A molecule or atom which is attracted to a negative charge and can accept a lone pair of electrons to form a covalent bond.

Question 4

How are free radicals formed?

Answer 4

Free radicals are formed when a covalent bond splits to return to electrons to their atoms. This is homolytic fission. It takes lots of energy to happen so it needs either UV light or temperatures of about 300 degrees C.

Question 5

Initiation

Answer 5

The free radical is formed. Cl–2Cl.

Question 6

propagation

Answer 6

Steps that start and end with a free radica. The product starts to be formed. CH4+Cl.–.CH3+HCl
.CH3+Cl2–CH3Cl+Cl+

Question 7

Termination

Answer 7

Steps in which two free radicals react. There are no radicals in the products. 2Cl.–Cl2
2.CH3–C2H6
.CH3+Cl.–CH3Cl

Question 8

State the number of isomers of pentane that are saturated compounds.

Answer 8

five/5

Question 9

State how the structure of thene shows it is an unsaturated molecule.

Answer 9

It it because it has a carbon-carbon double bond.

Question 10

Describe how temperature affects the length of the alkene molecules produced.

Answer 10

Thermal cracking can be used to produce alkenes such as ethene from long chain alkanes. At higher temp the long chain molecules break near the end, the higher the temp the shorter the alkene molecules/the higher the proportion of short chain alkenes.

Question 11

Why is it useful to crack long chain alkanes obtained from crude oil.

Answer 11

Surplus of long chain alkanes. Cracking produces alkenes which are in high demand.

Question 12

Explain how organic peroxides are involved in the initiation stage of the free radical polymerisation of ethene.

Answer 12

Organic peroxides contain oxygen-oxygen single bonds. Which break easily to give free radicals/very reactive and form free radicals.

Question 13

Describe the propagation stages in this reaction.

Answer 13

Free radicals hits ethene molecules forming longer free radical.

Question 14

Describe the termination stages in this reaction.

Answer 14

Two free radicals hit each other producing a final molecule. Reaction stops as no free radicals formed to react.

Question 15

what is standard enthalpy of hydration?

Answer 15

The energy released when one mole of ions dissolves in water.

Question 16

what is standard enthalpy of formation?

Answer 16

The enthalpy change when one mole of a compound is formed from its elements under standard conditions.

Question 17

what is standard enthalpy of combustion?

Answer 17

The enthalpy change when one mole of an element or compound reacts completely with oxygen under standard conditions.

Question 18

What is enthalpy change?

Answer 18

Enthalpy is the amount of energy per amount of substance that is given out or taken in.
Exo= -
Endo= +

Question 19

What is Hess’ law?

Answer 19

The enthalpy change or a reaction is independent o9f the rout taken so long as the final and initial conditions are the same.

Question 20

What are the 5 steps in extracting Al2O3?

Answer 20

Step 1: crush the bauxite.
Step 2: react with NaOH
Step 3: the iron oxide and the titanium oxide are removed by filtrate.
Step 4: allow the solution to crystallise to for Al(OH)3.
Step 5: heat the Al(OH)3 to convert it to alumina (Al2O3).

Question 21

What is a transition metal?

Answer 21

A transition metal is one which forms one or more stable ions which have incompletely filled d orbitals. Can have variable oxidation states because because 4s and 3d electrons are available.

Question 22

What are characteristics and properties of transition metals?

Answer 22

Characteristics:
incomplete d subshell, variable oxidation states (ions with different charges), complex ion formation.
Properties:
catalysis, coloured compounds.

Question 23

What are complex ions?

Answer 23

complex ions are positively charged ions surrounded by a number of molecules or oppositely charged ions called ligands.

Question 24

What are ligands?

Answer 24

They are molecules with a lone pair such as water or ammonia. Ligands attach themselves to the central ion by using a lone pair of electrons to form a dative bond (both electrons donated by one molecule to form a covalent bond). They also for complex ions.

Question 25

What is the stage to make vanadium oxide V?

Answer 25

stage 1: the sulfur dioxide is made. and is mixed with excess air.
Stage 2: sulphur trioxide is made.
Stage 3: sulfur trioxide is converted into sulfuric acid. and the sulfur trioxide is dissolved in a concentrated sulfuric acid.

Question 26

Info on Homogenous.

Answer 26

same phase as reactants. The transition metal is oxidised by one reactant to a higher oxidation state. This is then reduced back to the original form by reaction with the other reactant.

Question 27

info on heterogenous.

Answer 27

Different phase than reactants. Absorbs onto the surface of the site of the catalyst. With the reactants connected to the catalyst, the reaction occurs faster when reactants are absorbed onto the surface the bonds are weakened, this acts to lower the activation energy.

Question 28

how do transition metals work as catalysts?

Answer 28

Speeds up a reaction, lowers activation energy and they are able to change oxidation states so they have a variable oxidation states.

Question 29

What is the correct bond angle in methane?

Answer 29

109.5 degrees

Question 30

how many pi and sigma bonds are in a carbon to carbon double bond?

Answer 30

1 sigma and 1 pi

Question 31

what is the function of the membrane in the cell?

Answer 31

Membrane keeps chlorine (gas) separate from {hydrogen (gas). Chlorine will not be able to react with
{hydrogen. Membrane allows {Na+ / positive ions
cations} to pass through. Membrane does not allow {Cl-
negative ions to pass through.

Question 32

Describe how the water molecules are bonded to the vanadium (III) ion.

Answer 32

Lone pair of electrons donated /dative covalent bond. From water / ligand / oxygen (atom)
to vanadium(III) (ion).

Question 33

What is the chemical formula for alumina?

Answer 33

Al2O3

Question 34

what substance is used to dissolve alumina?

Answer 34

Cryolite

Question 35

The melting point of alumina is 2072°C.

Explain why the alumina is dissolved rather than melted before it is electrolysed.

Answer 35

Dissolving lowers the melting point and less energy is required so it will be more efficient.

Question 36

What is the pH of a basic metal hydroxide solution?

Answer 36

pH 10

Question 37

Sodium hydroxide is a base and an alkali.
Copper hydroxide is a base but not an alkali.
Give the reason why sodium hydroxide is an alkali but copper hydroxide is not.

Answer 37

Sodium hydroxide can dissolve in water.

Question 38

Manganese (IV) oxide is a transition metal compound.
It can be used as a catalyst to speed up reactions.
Explain why manganese (IV) oxide can act as a catalyst.

Answer 38

It has incomplete filled 3d energy levels. It has a variable oxidation states so it can be reduced and oxidised back again and lowers activation energy.

Question 39

Alkanes contain sigma (σ) bonds.
Alkenes contain both sigma (σ) and pi (π) bonds.
Explain, in terms of sigma and pi bonds, why alkenes are more reactive than alkanes.

Answer 39

A pi bond is weaker than a sigma bond. They overlap between atomic orbitals in pi bond is only partial. Electrons in pi bonds are further away from attraction of the nuclei so less energy needed to break the pi bond.