9.4.1 HSC Questions

2001 Q25 - Generally well answered but make sure you include:
* NOX is produced in all combustion engines - even with  optimal fuel:air ratios - however if there is excess air (oxygen) then the production of NOX increases.
* If you are going to present a combustion equation  -make sure it is BALANCED!
* Note that complete combustion also gives optimal energy output & fuel efficiency
* Actually say that insufficient oxygen causes incomplete combustion  - this was overlooked in a few of your answers
* Finally - to answer the Q - you must say why you need to monitor the products - ie by monitoring what chemicals are produced in the exhaust the conditions of combustion can be altered to add more oxygen (If C and CO are produced) or less oxygen (if excessive NOX produced) and thus increase fuel effieicncy and decrease pollution.

2012 Q33  - Generally well answered but make sure you include:

* The correct cell chemistry and reactions - this will always lose marks
* That the dry and silver cells are non-rechargeable and thus contribute to bulk landfill
* A full ASSESSMENT ie introduction to the chemistry and chemicals of the cell, positives of collaborating,  consequences of not collaborating (-ves?) and a clear judgement at the end - even labelling it'judgement' is a good idea so the marker won't miss it.
* Actually say specifically what the chemists who are collaborating do - don't waffle - just get to the point eg. Analytical chemists might analyse the soil and rivers near the rubbish tip to determine the concentration of (Zn - using AAS? and H+ - using a probe), they would communicate this with Environmental Chemists who would investigate the impact of these concentrations. They both might need to collaborate with Research chemists to determine a way to halt the spread of pollution. The research chemist may collaborate with industrial chemists to determine new ways of producing or packaging or recycling the cell. Electro-chemists would be involved in any research to manufacture new cells which are less harmful and rechargeable...