OCR A LEVEL ORGANIC CHEMISTRY YEAR 12 WITH VERIFIED QUESTIONS AND ANSWERS

OCR A LEVEL ORGANIC CHEMISTRY YEAR 12 WITH VERIFIED 
QUESTIONS AND ANSWERS

What is the melting and boiling points of alkanes like? - ANSWER--as chain length 
increases so does the strength of the intermolecular forces as there is greater 
surface area for contact between molecules and hence stronger london forces 
and therefore the melting/boiling points are highr for longer chain.
What is a structura/chain isomer? - ANSWER--Same molecular formula but a 
different structural formula
What are the rules with structural isomers? - ANSWER--Affect carbon chain 
length
-Alkyl side chain cannot be on the first carbon - the overall carbon chain length 
must remain the same
-Cyclic alkanes are not structural isomers of alkanes (they a are structural 
isomers of alkenes)
What are cycloalkanes? - ANSWER-alkanes in which the carbon atoms are 
arranged in a ring, or cyclic, structure
general formula CnH2n
What is the combustion of an alkane? - ANSWER--The reaction of the alkane with 
O2
-Exothermic
When does complete combustion take place? - ANSWER--When there is excess 
oxygen available
What are biodegradable plastics? - ANSWER--Broken down by enzymes
What are photodegradable plastics? - ANSWER--Broken down by U.V. Light
What is the general formula of alkanes? - ANSWER-CnH2n+2
Are alkanes saturated or unsaturated and why? - ANSWER--Saturated
-Each carbon atom forms four strong covalent, single, sigma bonds around it
Are alkanes polar or non-polar and why and how does this affect their solubility 
and reactivity? - ANSWER-The electronegativities of carbon and hydrogen are 
very similar so the C-H sigma (σ) bonds are non-polar
As a result of this, alkanes are nonpolar molecules and have no partial positive or 
negative charges (δ+ and δ- respectively)Alkanes therefore do not react with 
polar reagentsThey have no electron-deficient areas to attract nucleophilesAnd 
also lack electron-rich areas to attract electrophiles
What are the products of complete combustion? - ANSWER--CO2 and H2O
How do you balance alkane combustion equations? - ANSWER-1. C
2. H
3. O
How does the energy required/released in complete combustion change with 
increasing carbon chain length? - ANSWER--More energy is released to from the 
products
-More energy is required (to break the bonds in the reactants - activation 
energy), therefore it is harder to burn
When does incomplete comubstion take place? - ANSWER--When there is a limited 
supply of oxygen
What are the products of incomplete combustion? - ANSWER--CO and H2O
What is the problem with carbon monoxide? - ANSWER--It is highly toxic
-It binds irreversibally to the haemglobin in your red blood cells forming 
carboxyhaemglobin
-Less O2 is transported around the body
When is incomplete combustion more likely to take place and what also may be 
produced? - ANSWER--With longer chain alkanes (higher activation energy and 
react with more O2)
-Pure Carbon (soot) may be produced as a product of incomplete combustion
What additional products may be produced from impurities in the fuel 
(complete/incomplete combustion)? - ANSWER--SO2 and NOx
-They may be produced as a result of the combustion of Sulphur and Nitrogen 
impurities in the fuel
-The two products both contribute towards acid rain
What is the effect of and solution to CO2? - ANSWER--Global warming
-Use more carbon neutral fuel sources such as biofuels
What is the effect of and solution to H2O? - ANSWER--Global warming
-No solution
What is the effect of and solution to SO2? - ANSWER--Acid rain:
2SO2 + O2 - 2SO3
SO3 + H2O - H2SO4
-Carry out desulfurisation using CaO/CaCO3
CaO + SO2 - CaSO3 (calcium sulfite)
CaCO3 + SO2 - CaSO3 + CO2 (not as good because CO2 is produced)
What is the effect of and solution to NO? - ANSWER--Acid rain (HNO3)
-Catalytic converters:
2CO + 2NO - 2CO2 + N2
What is the effect of and solution to CO? - ANSWER--Smog and health issues
-Catalytic converters:
2NO + 2CO - 2CO2 + N2