Organic

Question 1

State the general formula for an alkane

Answer 1

CnH2n+2

Question 2

Define a hydrocarbon

Answer 2

A compound that contains hydrogen and carbon atoms ONLY

Question 3

What does saturated mean?

Answer 3

A hydrocarbon which contains only single C-C bonds, when the C has the max n. of single bonds

Question 4

Are alkanes polar or non-polar?

Answer 4

Non-polar

Question 5

Do branched or straight chained molecules have a higher bp?

Answer 5

Straight chained= more surface area = increased strength of vdwf

Question 6

What is crude oil?

Answer 6

A mixture of mainly alkane hydrocarbon chains that can be separated
-Dark yellow/black sticky liquid found under the earth

Question 7

Define fractional distillation

Answer 7

The continual evaporation and condensation of a mixture causing the molecules to separate because of the difference in their bp

Question 8

What is a fraction within an fractional distillation?

Answer 8

A group of molecules that have SIMILAR bp and are removed at the same level of a fractionating coloumn
-Similar chain length

Question 9

Describe the process of fractional distillation

Answer 9

1. Crude oil is heated and vaporised in a furnace until a portion changes state
2. Liquid vapour mixture is passed up a fractioning tower (cooler at top than bottom) with a temp gradient
3. When a substance reaches a layer which is cool enough, it condenses and is piped off
4. Shorter chain length molecules are condensed at top of the tower where its cooler

Question 10

Define cracking

Answer 10

The process where long chain hydrocarbon mol. are broken into shorter chain molecules which are higher in demand

Question 11

Why do we need to crack long chains?

Answer 11

To obtain shorter chains:

• Better fuels
• Higher in demand
• More useful

Question 12

Describe the conditions for thermal cracking

Answer 12

Temp: 1000-1200K
Press: 70atm
Catalyst: no

Question 13

Describe the physical properties of alkanes

Answer 13

Insoluble in water but will dissolve in other non-polar substances

Question 14

Describe the conditions needed for catalytic cracking

Answer 14

Temp: 800-1000K
Pressure: 1-2 atm
Catalyst: Zeolite

Question 15

Describe the features of the catalyst used in catalytic cracking

Answer 15

Zeolite

-Acidic material w a honeycomb structure* gives a large SA for high r of r

Question 16

What products are produced with catalytic cracking?

Answer 16

-Branched alkanes, cycloalkanes, aromatic compounds, motor fuels

Question 17

Write the equation for the complete combustion of methane in oxygen

Answer 17

CH4 (g) + 2O2 (g) –> CO2 (g) + 2H2O (g)

Question 18

Write the equation for the incomplete combustion of methane in oxygen

Answer 18

CH4 (g) + 1/2 O2 (g) —-> CO (g) + 2 H2O (g)

Question 19

What are the common products of thermal cracking?

Answer 19

-High percentage of alkenes + some short chain alkanes

Question 20

If the combustion is under very limited supply of oxygen what forms?

Answer 20

Soot

Question 21

Write the equation involving the incomplete combustion of butane under very limited supply of oxygen

Answer 21

C4H10 (g) + 2 1/2 O2 (g) —-> 4 C (s) + 5 H2O (g)

Question 22

What by products are made in the combustion of an internal combustion engine?

Answer 22

-Nitrogen oxides (NO and NO2)
-Sulfur dioxide
-

Question 23

What are the compounds present in the combustion mixture of a engine?

Answer 23

CO2, C, CO , NO2, NO, SO2, H20 , hydroca

Question 24

What is the cause of acid rain?

Answer 24

Sulfur dioxide gas produced when impurities in fossil fuels are burned

-Sulfur dioxide reacts w water in air to produce sulfurous acid and then oxidises to form sulfuric acid

Question 25

Write the overall equation to form acid rain from sulfur dioxide

Answer 25

SO2 (g) + H20 + 1/2 O2 (g) —–> H2SO4 (aq)

Question 26

What causes photochemical smog?

Answer 26

Toxic gases and small particles in air close to surface of earth react
-For irritated eyes and nasal congestions

Question 27

What is the function of a catalytic converter?

Answer 27

To reduce the amount of CO, nitrous oxides and unburnt hydrocarbons released by internal combustion

• By converting them into less toxic gases (e.g CO2, H2O)
• Made of honey comb ceramic material covered in thin layer of catalyst

-As gases pass over the catalyst they react with each other producing less polluting products

Question 28

What catalysts are used in the catalytic converter?

Answer 28

Platinum and rhodium

Question 29

What substances are used to remove sulfur?

Answer 29

-Calcium oxide and calcium carbonate to produce calcium sulphite (CaSO3)

Question 30

State what is meant by a chain isomer

Answer 30

-Same molecular formula but differ in length of the carbon chain

Question 31

State what is mean by a positional isomer

Answer 31

Same molecular formula and functional group but difference in position of the function group on c chain

Question 32

State what is meant by a functional group isomer

Answer 32

Same molecular formula but different functional group

Question 33

Suggest the problems associated with isomerism ( 3 marks)

Answer 33

• Difficult to identify an unknown organic molecule because there may be more than one structure for the same molecular formula
• Mass spectrometry can be used to tell more info about the structure