DF 6

Question 1

What alkenes are gases?

Answer 1

Ethene, propane and butene

Question 2

What alkenes are liquids?

Answer 2

Ones with 5-14 carbons

Question 3

What alkenes are solid?

Answer 3

ones with 15 or more carbons

Question 4

General formula of alkenes

Answer 4

CnH2n

Question 5

What is a electrophile?

Answer 5

Species attracted to negative charge

Question 6

What type of bonds does the double bond in an alkene contain?

Answer 6

One sigma and one pi bond

Question 7

What is a carbocation?

Answer 7

An ion with a positively charged carbon atom

Question 8

What does benzene look like?

Answer 8

Hexagon with a circle in the middle

Question 9

Example of a name of an alkene with 2 double bonds

Answer 9

PentA -1,4- DIene

Question 10

Which type of bond breaks first?

Answer 10

The pi bond as it has a lower enthalpy than the sigma bond

Question 11

How is the pi bond formed?

Answer 11

Formed below and above the plane of the carbon atoms
by a sideways overlap of P orbitals

Question 12

explain why some alkenes can have E or Z isomers

Answer 12

the pi-bond fixes the carbon atoms in position
preventing rotation around the double bond

Question 13

explain why the bond angles in alkenes are 120o

Answer 13

there are 3 regions of charge on each carbon in the double bond
these will repel each other as far as possible to minimise repulsions
forming a trigonal planar shape

Question 14

explain why alkenes are attacked by electrophiles

Answer 14

Because they contain a double bond which is an area of high electron density due to the orbital overlap

Question 15

explain why alkenes undergo addition reactions

Answer 15

they are able to donate an electron pair to an electrophile
Which breaks the pi-bond
and add a small molecule to form a new product molecule

Question 16

explain why ethene is a planar molecule

Answer 16

each carbon of the double bond has a trigonal planar shape
these are fixed in place by the pi bond
Which prevents rotation

Question 17

Reagents needed for the reaction of propene and bromine

Answer 17

Propane and bromine water with no special conditions

Question 18

Reagents needed for the reaction of propene and hydrogen

Answer 18

Propene gas, hydrogen gas, 150 degrees Celsius, Nickel catalyst

Question 19

Why are catalyst used in industry?

Answer 19

• Speeding up the process
• Reducing the amount of energy required
• improving percentage yield

Question 20

How does catalyst poisoning occur?

Answer 20

• Poisoned molecules are more strongly ADsorbed than the reactants
• Poisoned molecules ADsorb onto the catalyst surface but do not react
• No space for reactants to attach to the surface
• catalyst becomes inactive

Question 21

What are homogenous catalysts?

Answer 21

catalyst which are in the same physical state as the reactant

Question 22

How to draw enthalpy diagram for adding a catalyst?

Answer 22

Large curve - Ea - without catalyst
Small curve - Ec - with catalyst

Question 23

Describe what happens in an ethene + hydrogen reaction with a catalyst

Answer 23

• Hydrogen adsorbs onto the catalyst surface
• ethen adsorbs onto the catalyst surface
• Double bond in ethene weakens then breaks
• allowing new bonds with hydrogen to be formed
• the newly formed at hand is released from the surface and diffuses away