Alkanes

Question 1

Saturated definition

Answer 1

Molecules containing single bonds only

Question 2

Hydrocarbons

Answer 2

Molecules containing carbon and hydrogen only

Question 3

Physical properties

Answer 3

The boiling point increases with the chain length because with a larger molecule the induced dipole dipole attractions between molecules becomes stronger due to the more electros. The longer the chain, the bigger the molecule and the more electrons.
Boiling point also increases with branching- more surface contact between molecules of pentane so IDD is stronger

Question 4

Fractional distillation

Answer 4

Fraction definition: A group of hydrocarbons with similair boiling points.
Seperate hydrocarbons based on their differnt boiling points
Crude oil is heated and vaporised as it enters the column at the bottom, the mixture of hydrocarbons have differnt boiling points (which depend on chain length and branching), hotter at the bottom, larger and longer molecules condesen and are collected first a the bottom.

Question 5

Cracking

Answer 5

purpose- to produce more useful, shorter chain molecules that are in higher demand. Conditions: 700-1200K, 7000KPA
catayltic cracking: produces a high % of branched alkanes and cycloalkanes. &20 K, 100KPA and zeolite.

Question 6

Combustion

Answer 6

Complete- forms CO2 and water
Incomplete- produces CO gas or C solid

Question 7

SO2

Answer 7

S(s) + O2–> SO2 (g)
dissolved to form acid rain:
SO2(g) + 1/2O2(g) +H20 –> H2SO4 (l)

Question 8

Nitrogen oxides

Answer 8

requires high temperature, nitrigen react with O2.
N2(g) + O2(g) –> 2NO (g)
2NO(g) + O2 –> 2NO2(g)
dissolved to form acid rain
4NO2(g) + 2H2O(l) + O2 –> 4HNO3

Question 9

Methods to reduce pollution

Answer 9

Flue gas desulfurisation
CaO(s) +2H2O +SO2 +1/2O2 –> CaSO4 + 2H2O
alternative:
CaCO3 + 1/2O2 –> CaSO4
catalytic converter:
Honeycomb structure inceases the surface area, increasing the reaction rate of the reactions.
2NO(g) +2CO (g) –> N2(g) +2CO2(g)
C8H18 +25NO –> 8CO2 + 9H2O +12.5N