Alkanes And Alkenes

Question 1

Tell me about thermal cracking

Answer 1

Takes place at a high temperature and high pressure (up to 1000 degrees Celsius and 70atm)

Produces a lot of alkenes

The alkenes produced used to make polymers

Question 2

Tell me about Catalytic cracking

Answer 2

Uses a zeolite catalyst at a slight pressure and high temperature

Produces aromatic hydrocarbons

Cuts costs

Question 3

What is a free radical

Answer 3

Particle with unpaired electron
Happens when covalent bonds split equally

Question 4

What type of hydrocarbon is an alkene

Answer 4

Unstaturated hydrocarbon

Question 5

What happens when you add a hydrogen halide to unsymmetrical alkenes

Answer 5

It forms two products

Question 6

How can a alcohol form an alkene

Answer 6

An alcohol has to be dehydrated to form an alkene. The water should be elimated use a dehydration reaction

Question 7

How to produce cyclohexane from cyclohexanol

Answer 7

add conc H2So4 and. H3PO4 to a round bottom flask containing cyclohexanol.

Mix solution by swirling flask

Add carborundum chips so mixture boils calm

Gently heated : water bath
Warm gas rise condenser will turn it to liquid

Product collected in cooled flask

Remove impurities by using separating funnel+ water to dissolve impurities

Let settle into layers

Drain cyclohexene into round bottomed flask

Add anhydrous cacl2 let mix dry

Distil again

Question 8

How to oxides an alcohol

Answer 8

Use acidified potassium dichromate

Question 9

What happens when primary alcohols are oxidised

Answer 9

Aldehyde is formed then if oxidised agin turns to carboxylic acid

Question 10

What happens when secondary alcohols are oxidised

Answer 10

Secondary Oxidises to ketone

Question 11

Describe aldehyde

Answer 11

Has a hydrogen and one alkyl group attached to the carbonyl atom

Suffix is -al

Question 12

Describe ketone

Answer 12

They have 2 alkyl groups attached to the carbonyl carbon atom
Suffix is -one

Question 13

Describe Carboxylic group

Answer 13

Have a COOH group at end of carbon chain
-oic acid

Question 14

Describe oxidation of primary alcohol into aldehyde into carboxylic acid

Answer 14

Gently heat with potassium dichromate and sulfuric acid produces ethanal

Get aldehyde only, gets out as soon as it forms use distillation apparatus

Carboxylic acid production alcohol vigorously oxidised. Excess oxidising agent heated under reflux

Question 15

What does it me man to heat under reflux

Answer 15

You can inc the temp of an organic reaction without losing volatile solvents reactants or products.

Question 16

How to test for primary secondary or tertiary alcohol using acidified potassium dichromate

Answer 16

Add acidified potassium dichromate
Warm in hot water bath
Primary orange goes green
Secondary orange goes green
Tertiary’s nothing

Question 17

Feelings solution and Benedict’s solution

Answer 17

Add 2 cm^3 of Fehling’s or Benedict’s solution to a test tube.
(Whichever one you use, it should be a clear blue solution.)

Add 5 drops of the aldehyde or ketone to the test tube.

Put the test tube in a hot water bath to warm it for a few minutes

.
ALDEHYDE - the blue solution will give
a brick red precipitate.

KETONE - nothing happens.

Question 18

Test for ketone and aldehyde functional groups

Answer 18

Put 2 cm of 0.10 mol dm-3 silver nitrate solution in a test tube.
colourless silver nitrate solution

Add a few drops of dilute sodium hydroxide solution.
A light brown precipitate should form.

Add drops of dilute ammonia solution until the brown
precipitate dissolves completely.

OR add tollens solution

Place the test tube in a hot water bath and add 10 drops of aldehyde or ketone.

Wait for a few minutes.

ALDEHYDE - a silver mirror (a thin coating of silver) forms on the walls of the test tube.

KETONE - nothing happens.

Question 19

Explain
How to use a spectroscopic technique.

Answer 19

Distinguishing the acids

using IR spectroscopy to distinguish the two acids
use finger-print region of IR spectrum
look for exact match to spectra of known compounds

Question 20

Fermentation of glucose equations

Answer 20

6CO2 + 6H2O → C6H12O6 + 6O2

С6Н1206 → 2C2H5OH + 2CO

2C2H5OH + 602 → 4CO2 + 6H2O

Question 21

Importance of percentage yield?

Answer 21

Getting as much product as possible in reaction

Question 22

Importance of atom economy

Answer 22

Minimising the amount of by products

Question 23

How to measure water without balance

Answer 23

Use density of water (1gcm^-3) and use a fixed volume density