Alkanes

Question 1

Definition of hydrocarbons

Answer 1

A compound with hydrogen and carbon atoms only

Question 2

Definition of saturated

Answer 2

A compound with single carbon bonds only

Question 3

Definition of fraction

Answer 3

A mixture of compounds with similar sized molecules and similar boiling points

Question 4

Trend in homologous series

Answer 4

Same chemical properties
Gradual change in physical properties

Question 5

Boiling points of alkanes

Answer 5

As chain length of alkanes increases the boiling point increases as more electrons so greater Van der walls forces of attraction
More branching decreases the boiling point as less surface contact between molecules

Question 6

Definition of crude oil

Answer 6

Mixture of hydrocarbons with different chain lengths which determine their boiling point

Question 7

Steps of fractional distillation

Answer 7

1. Crude oil is vapour and enters column.
2. Hydrocarbons have different boiling points depending on their chain length and branching.
3. Column is cool at the top and hot at the bottom.
4. Small chain molecules condense on the top of the column whereas large chain molecules condense at the bottom of the column.

Question 8

Thermal cracking

Answer 8

High temperature of 900 Celsius and high pressure of 7000 kpa
Produces one alkane with many alkenes

Question 9

Catalytic cracking

Answer 9

High temperature of 450 Celsius and slight pressure of 100 kPa
Zeolite catalyst
Branched alkanes and cycloalkanes/ aromatics

Question 10

Complete combustion

Answer 10

Uses oxygen
Produces carbon dioxide and water

Question 11

Incomplete combustion

Answer 11

Uses oxygen
Produces carbon monoxide (g) or carbon (s) and water

Question 12

How is sulphur dioxide made?/ H2SO4

Answer 12

Sulfer is an impurity made by crude oil and when crude oil burns sulphur burns with oxygen forming SO2. SO2 dissolves in rain water forming H2SO4

Question 13

Equation for sulphur dioxide dissolving in rainwater

Answer 13

SO2+ 02+H20=H2SO4

Question 14

How is nitrogen dioxide formed?/ HNO3

Answer 14

Car engines convert nitrogen in the air into nitrogen dioxide at high temperatures
N2 +02=2N0
Nitrogen dioxide, then dissolves in rainwater to form acidic rain which is HNO3
NO2+H20+02=HNO

Question 15

What are catalytic converters made of?

Answer 15

They are made of platinum or rhodium
They have a honeycomb structure which provides a large surface area to convert harmful gases into less harmful gases

Question 16

Removal of carbon monoxide and nitrogen monoxide

Answer 16

NO+CO=N2 +С02

Question 17

Removal of unburned hydrocarbons and nitrogen monoxide

Answer 17

C8H18 + 25NO→8CO2 + 9H20 + 12.5N2

Question 18

There are two methods of desulferation:

Answer 18

( flue gas is SO2 ) 1. A mixture of calcium oxide and water is sprayed into flu gas which reacts to make solid calcium sulphate.
CaO+H2O+SO2+02=CaS04.2H20
2. Another way is to pass the flu gas through calcium carbonate, which produces solid calcium sulphate.
CaCO3+02+S02=CaSO4+CO2r