Topic 6

Question 1

What type of reaction is where alcohols react with concentrated phosphoric acid to form alkenes?

Answer 1

ELIMINATION

Question 2

What is meant by stereoisomers?

Answer 2

• compounds with same structural formula

Where the atoms have a different displayed formula

Question 3

CH3CH2CH2CH2OH reacts with the oxidising agent potassium dichromate(VI) in dilute sulfuric acid.
Two organic products can be formed, depending on the conditions.
Write a balanced equation for the formation of one of these products, giving its name and the condition required to achieve this product in high yield.
Use [O] in the equation to represent each oxygen atom from the oxidising agent.
Equation

Name ……………………………………………………………………………………………………………………………
Condition ………………………………………………………………………………………………………………………

Answer 3

CH3CH2CH2CH2OH + 2[O] -> CH3CH2CH2COOH+ H2O

BUTANOIC ACID

HEAT UNDER REFLUX

Question 4

One reason why the yield calculated is less than 100%

Answer 4

• side reactions
• incomplete
• transfer losses

Question 5

Deduce a chemical test for a C=C bond

Answer 5

Bromine water

Orange/ brown goes colourless

Question 6

Devise a procedure to obtain a pure dry sample of cyclohexane from the distillate

Answer 6

• separate cyclohexane from water using SEPARATING FUNNEL
• remove AQUEOUS layer as it has a higher density
• use a drying agent (metal Sulfates)
• separate cyclohexene from drying agent
• redistil product (by FILTRATION OR DECANTATION)

-collect after boiling at temp between 80-86

Question 7

Using apparatus for distillation instead of reflux is not an efficient way to produce ethanoic acid from ethanol. Explain why.

Answer 7

Ethanol would be OXIDISED to ethanal

Ethanal has a LOW BP

Question 8

Give a reason for the addition of ethanol to each test tube (1)

Answer 8

Increases solubility or dissolves the halogenoalkane

Question 9

Give a reason why the test tubes were left in the water bath for 5 mins before adding the halogenoalkanes (1)

Answer 9

Allow solutions to equillbrate and reach required temperature

Question 10

Explain why halide ions are present in the mixture containing a halogenoalkane which only has covalent bonds (2)

Answer 10

(Halogenoalkane) hydrolysed by water

C-Hal bond breaks (heterolytically producing ions)

Question 11

Write the ionic equation with state symbols for the reaction involving silver nitrate in test tube X (1-chlorobutane)

Answer 11

Ag+ (aq) + Cl- (aq) -> AgCl (s)

Question 12

Which of the following DOES NOT act as a nucleophile

• HBr
• H2O
• NH3
• CN-

Answer 12

HBr

Question 13

what type of reaction occurs when propene reacts with HCl?

Answer 13

electrophilic addition

Question 14

Q: NAME the reagents used in reaction 1

chloropropane can react to form organic products as shown in the reaction scheme:

CH3 CH CH2 Reaction 1

CH3 CH2 CH2 C N
Reaction 2

CH3CH2 CH2 Cl Reaction 3

concentrated ammonia solution heated in a sealed tube

CH3 CH2 CH2 NH2

Answer 14

Reagent: NaOH/ KOH
condition: ethanol and heat

Question 15

ii) Identify a suitable reagent for Reaction 2 and include a reason why this is a particularly useful type of reaction in organic chemistry. (2)

chloropropane can react to form organic products as shown in the reaction scheme:

CH3 CH CH2 Reaction 1
CH3 CH2 CH2 C N Reaction 2
CH3 CH2 CH2 Cl Reaction 3
concentrated ammonia solution heated in a sealed tube=
CH3 CH2 CH2 NH2

Answer 15

KCN/NaCN /potassium cyanide / sodium cyanide (1)

Reason:
increases the number of carbon atoms in the carbon chain/ length of carbon chain

Question 16

Explain why, in reaction 3, the reagents are HEATED in a sealed container

chloropropane can react to form organic products as shown in the reaction scheme:

CH3 CH CH2 Reaction 1
CH3 CH2 CH2 CN Reaction 2
CH3 CH2 CH2 Cl Reaction 3
concentrated ammonia solution heated in a sealed tube
CH3 CH2 CH2 NH2

Answer 16

heating increases rate (of reaction) (1)

no sealed tube would result in loss of ammonia (gas)/ reactants / gas

Question 17

Write the structural formula of the product that will be formed if 1-chloropropane is refluxed with aqueous potassium hydroxide solution

Answer 17

CH3 CH2 CH2 OH

Question 18

explain why isomers of hexane have lower boiling temps and so are found in the petrol fraction (3)

Answer 18

isomers have branched chains

branched chains have lower SA

Intermolecular forces are weaker

Question 19

explain the 2 major reasons for cracking hydrocarbons (3)

Answer 19

SHORTER chain alkanes AND alkenes formed

alkenes used to make polymers/plastics

shorter chain alkanes are more in demand

Question 20

describe 2 charactersitics of the homologous series

Answer 20

same general formula

same functional group

Question 21

what is meant by structural isomer?

Answer 21

same molecular formula
different displayed formula

Question 22

state the purpose of adding ethanol to test tubes

Answer 22

to dissolve BOTH the laogenoalkane and water

Question 23

give one reason why the test tubes are placed in the same beaker of hot water

Answer 23

same temperature

Question 24

give one reason why the test tubes were shaken after the addition of aq silver nitrate

Answer 24

ensure reactants are mixed thoroughly

Question 25

state how the halogen atom present in each halogenoalkane can be identified from observations in the experiment

Answer 25

CL- white
Br - cream
I - yellow

Question 26

identify further reagents that can be added to confirm the identity of the halogen atom present in each halogenoalkane (2)

Answer 26

dilute AND conc ammonia solution
silver chloride, silver bromide and silver iodide