8. Alkanes
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Alkanes definition
saturated hydrocarbon that contain only C-C and C-H single bonds
Saturated definition
compound contains only single bonds
hydrocarbon definition
comounds containing only C and H
What is the bpt of an alkane is determined by?
• C-C chain length • Number of branches (side chains)
Why does the bpt of an alkanes increase with chain length?
• have I.D.D foces between molecules • strength of attraction increases with increasing size of molecule and number of e- • longer the C chai, the bigger the molecule and the more e-
Why does pentane have a higher bpt than 2,2-dimethylpropane?
• 2,2-dimethylpropane has more branches than pentane • more surface contact between molecules of pentane • induced dipole-dipole attractions between molecules of pentane are stronger
Describe the essential features of a fractional distillation that enable the crude oil to be separated into fractions
• crude oil is heated to vaporise and enters the column • hydrocarbons have diff bpts that depend on their size/Mr/C chain length • column is cooler at the top, hotter at bottom • larger molecules iwth higher bpts condense at the bottom
Thermal Cracking conditions
• high temperature • high pressure
Example: Thermal Cracking 1 mole of compound Y is cracked to produce 2 moles of ethene, 1 mole of but-1-ene and 1 mole of octane (C8H18). Deduce the molecular formula of Y.
C16H34 → 2 C2H4 + C4H8 + C8H18
Conditions for catalytic cracking
• high temperature (lower than catalytic cracking) • slight pressure • zeolite catalyst
Equation for SO2(g) dissolving in O2 forming a very acidic solution of H2S04, known as acid rain
SO2(g) + 0.5O2(g) + H2O (l) → H2SO4 (aq)
Formation of nitric oxide (NO)
N2 (g) + O2 (g) → 2NO (g)
Formation of nitrogen dioxide (NO2)
2NO (g) + O2 (g) → 2NO2 (g)
Equation of NO2 dissolves in rainwater to produce an acidic solution (HNO3)
4NO2 (g) + 2H2O (l) +O2 (g) → 4HNO3 (aq)
Flue Gas Desulfurisation Equation for when a mixture of CaO and water is sprayed into the flue gas which reacts to form solid calcium sulphate
CaO (s) + 2H2O (l) + SO2 (g) + 0.5 O2 (g) → CaSO4.H2O (s)
Flue Gas Desulphurisation Equation for when flue gas is passed through CaCO3, producing calcium sulphate
CaCO3 (s) + 0.5 O2 (g) + SO2 (g) → CaSO4 (s) + CO2 (g)
Catalytic Converter Removal of CO and NO Equation Catalytic Converters are made of platinum and thodium (are catalysts), honeycomb structure which increases S.A and rate of reaction
2NO (g) + 2CO(g) → N2 (g) + 2CO2 (g)
Catalytic Converter Removal of Unburnt Hydrocarbons and NO
C8H18 + 25NO → 8CO2 + 9H2O + 12.5N2