Chapter 13 alkenes

Question 1

State the catalyst needed for the reaction between hydrogen and alkenes (1)

Answer 1

Nickel

Question 2

What would you observe when bromine is addeded to an alkene (1)

Answer 2

bromine is decoulourised

Question 3

Name the reactants and conditions when an alcohol if formed from an aklene (1)

Answer 3

Steam and acid catalsyt

Question 4

State one advantage and one disadvantgage using combustion fro the diposal of waster polymer (2)

Answer 4

• advantage - energy production / energy used to produce electricity
• disadvantage - formation fo HCL/ products of combustion can cause acid rain
• formation of CO2/ gases that cause global warming
• formation of carbon monxoxide

Question 5

State the meaning of the term electrophile and suggest the formula of the electrophile formed from IBr (2)

Answer 5

• electron pair acceptor
• I+

Question 6

Explain why poly(propene) is a saturated hydrocarbon (1)

Answer 6

because molecule only contains only single C-C bond

Question 7

State the bond around each of the carbon atom in poly(propene) (1)

Answer 7

109.5

Question 8

Polymers can be processed by recycling Describe two other ways in which waste poly(propene) can be processed in a sutainable way (2)

Answer 8

• combustion for energy production
• use as organic feedstock

Question 9

State one particular problem with disposal of poly(2-chloropropene) by combusiton (1)

Answer 9

Formation of HCl
chlorine

Question 10

What is the catalyst for 2-chloropropene reacting with steam (1)

Answer 10

• acid
• H2SO4
• H3PO4

Question 11

State and explain the features of hex-2-ene molecule that lead to E/Z isomers (2)

Answer 11

• carbon to carbon double bond does not rotate has restricted rotation
• each carbon atom of the double bond attatched to two different groups / atoms

Question 12

What is the essentiall condition for alkene to react with H2O (2)

Answer 12

• steam
• acid catalyst

Question 13

Name the mechanism for addition reactions with alkenes (1)

Answer 13

electrophillic addition

Question 14

What is the general formula for alkenes (1)

Answer 14

CnH2n

Question 15

Describe one difference between the sigma bond and the pi bond (1)

Answer 15

• sigma bond is between bonding atoms nuclei and pi bond is above and below bonding atoms / nuclei
• sigma bond has direct/ head overlap of orbitals and pi bond has a sideways overlap
• pi bond has a lower bond enthlapy i weaker than sigma bond
• sigma bond has electron density betwen bonding atoms and pi bond has electron densirty above and below bonding atoms

Question 16

In step 2 1-bromopropane reacts with chlorine via radical substitution
Outline the meachnisms for the monochlorination of 1- bromopropane (C3H7Br)
State the essential condiions (6)

Answer 16

intitiation
* Cl2 - >2Cl. and UV
propogation
* C3H7Br + Cl - > C3H6Br + HCl
* C3H6Br + Cl2 ->C3H6BrCl + Cl
termination
* 2Cl. - > Cl2
* * C3H6Br + Cl -> C3H6BrCl
* “C3H6Br. -> C6H12Br2

Question 17

Radical substitution produces a mixture of organic products suggest two reasons why (2)

Answer 17

• further substitution, produces different termination products / more than one termination step
• substitutionat different points along the chain

Question 18

Give the formula of an acidic toxic gas that can form during the combustion of polymers (1)

Answer 18

HCl

Question 19

What is meant by the term structural isomers (1)

Answer 19

Compounds or molecule have the same molecular formula but differnt structural formula

Question 20

Suggest why 2-methylbut-2-ene is less soluble in water (2)

Answer 20

• does not contain Oh groups / not contain hydroxyl group/ not an alcohol
• not form hydrogen bonds with water

Question 21

Write an equation for the incineration of the monomer, chloroether with oxygen (1)

Answer 21

Ch2ChCl+2O2 -> CO + CO2+HCl + H2O

Question 22

Explain how sodium hydrogencarbonate removed hydrogen chloride (1)

Answer 22

Sodiumhydrogencarbonate neutralises HCl

Question 23

What doe a curly arrow represent in a reaction mechanism (1)

Answer 23

movement of a pair of electrons

Question 24

Pent-1-ene CH3CH2CH2CH=CH2 is an alkene with molecule formula C5H10 why does it not show steroisomerism (1)

Answer 24

One of the carbons of the C=C has two of the same gorupss attatched / has two hydrogen atoms attatched

Question 25

What is the general formula for alkyl group (1)

Answer 25

CnH2n+1

Question 26

Desscribe the test for the functional group in an alkene (1)

Answer 26

Bromine water is decolourised

Question 27

Describe how HCl is removed from the waste gases produced (1)

Answer 27

HCl gas is passed through an alkali/carbonate

Question 28

Sate an advantage of using polymers made from natural polymers except that it not produce toxic gas (1)

Answer 28

* reduced the dependency on finite resources * biodegradable * photodegradable

Question 29

Describe how a catalyst increases the rate of a chemical reaction (2)

Answer 29

* allowes the reaction to take an alternative reaction pathway with a lower activation energy * so that a greater proportion of molecules exceed the activation energy

Question 30

What is the best description for the bonding between carbon atoms in an ether molecule (1)

Answer 30

one sigma bond and one pi bond

Question 31

A student reacts with pent-2-ene with bromine in the labratory what compound is formed (1)

Answer 31

2,3-diobromopentane