2011 Chains, Energy and Resources Jun Flashcards
Why is this reaction exothermic
- Bond breaking absorbs energy AND bond forming releases energy
- More energy released than absorbed
What is meant by the term enthalpy change of combustion
- (Enthalpy change) when one mole of a substance
* Is completely combusted OR burns in excess oxygen
What is meant by the term functional group
• Group of atoms O
• That give a compound its (characteristic set of) reactions
•
At RTP, the first four members of the alcohol homologous series are liquids whereas the first four members of the alkane homologous seires are gases
- Alkanes have van der Waals’ intermolecular forces
- Alcohols have hydrogen bonds (and van der Waals’ forces)
- Hydrogen bonds are stronger (than van der Waals’ forces)
Methylpropan-1-ol has a lower boiling point than butan-1-ol
- Methylpropan-1-ol has weaker van der Waals’ forces (than butan-1-ol)
- Methylpropan-1-ol has less surface points of contact (than butan-1-ol)
- Methylpropan-1-ol has more branching (than butan-1-ol)
Explain the meaning of the term endothermic
• Reaction in which energy enters the system (from the
surroundings)
Explain the meaning of the term activation energy
• Activation energy is the minimum amount of energy needed for the reactants to react
Reaction in which nitrogen monoxide catalyses ozone depletion in the stratosphere
- 2NO + O2 -> 2NO2
- NO + O3 -> NO2 + O2
- NO2 + O -> NO + O
- Overall reaction is O3 + O -> 2O
Outline the use of infrared spectroscopy in identifying air polluntants
- To identify the functional groups (in pollutants) OR to identify the bonds (in pollutants)
- Match spectrum to known pollutants OR each pollutant will have a different spectrum
- Idea that you can measure the concentration or abundance of pollutants
Explain why some molecules show E/Z isomerism
- Non rotating (carbon–carbon) double bond
* Each carbon atom of the double bond attached to (two) different groups/atoms
