Chemistry Marathon v.1.0 (1 Viewer)

[doiyoubi]

Seeing there's a maths one, should the chemistry not have one as well
Rules are one person asks a question from the syllabus and the next person answers and posts a new one
I'll get it started then

Describe and assess the effectiveness of methods used to purify and sanitise mass water supplies

 

[pLuvia]

Methods of purifying water:
1. Screening - the water is sieved to removed any large matter such as twigs, fish, rocks etc
2. Aeration - the water is sprayed into the air to allow the surface area of the water to be enlarged and that in turn allows more oxygen to dissolve into the water
3. Flocculation - there are suspended particles in the water that don't settle to the bottom as easily due to repulsion between negative surfaces and so the particles are to coagulate to make the particles bigger so it can settle easier
4. Sedimentation - the coagulated particles are left to settle to the bottom and then are extracted from the water
5. Filtration - this water is then passed through a filter containing of sand and gravel to remove any particles, bacteria and coloured matter and the water that emerges should be clear
6. Chlorination - chlorine is added to the water to kill any existing microorganisms such as coliforms eg E. coli which is bacteria.
7. pH - buffers are added to alter the pH to an optimum pH of water which is around 7 - 8.5 which also prevents the corrosion of pipes
8. Fluoridation - fluorine is added to raise fluorine level to 1 ppm and to prevent tooth decay

The sand filtration removed a lot of matter which is not very costly and the chlorination removes many bacteria still in the water which is cost-effective too. However there are some microorganisms that may still be present in the water, one example is the mid 1998 the Giardia and Crytosporidium scare in sydney. Now there are better ways of purifying water using membrane filters which use the principle of reverse osmosis or ozone sterilisation but both are very costly

Next Question
Describe the Haber process and what are the uses of the products

 

[Riviet]

Describe the Haber process and what are the uses of the products

The Haber process is an industrial process in which ammonia is synthesised from Nitrogen and Hydrogen gas:
N_2(g) + 3H_2(g) <=> 2NH_3(g)
A moderate temperature of about 400^oC and total pressure of about 250atm is used to optimise the yield of product and time taken. A magnetite catalyst (Fe₃0₄) is used to lower the activation energy, ie reduces the heat required for the reaction, which helps to increase the yield.
Ammonia is used to make fertilisers, household cleaning agents and detergents, as well as plastics and explosives.

*Suggestion: instead of posting up questions that involve recalling information, ie short answer/extended response questions, maybe we could try some calculation or multiple choice questions. This may make the thread more active and encourage more to participate in the marathon. If you really want though, you are free to post those longer response/short answer questions.*

Next Question:
A reagent bottle on a laboratory shelf contains a colourless liquid and has the label:

C₂H₅OH
(95%)

Which of the following is the most important piece of safety equipment when using this substance?

(A) eye protection
(B) a fire blanket
(C) gloves and apron
(D) a fume hood

 

[Sparcod]

Ethanol?
You need eye protection. Wear glasses. You also need to take care in handling.

Next Question:
Identify the importance of and methods of analysing hardness, turbidity, acidity, dissolved oxygen and biochemical oxygen demand in water samples.

 

[Riviet]

Ethanol?
You need eye protection. Wear glasses. You also need to take care in handling.

Eye protection is incorrect for this question. What if a fire starts? How could you put out a flame with eye protection?

 

[Forbidden.]

Are we asking questions from the Chemistry Preliminary or HSC syllabus ?

 

[Riviet]

Are we asking questions from the Chemistry Preliminary or HSC syllabus ?

It's primarily based on the HSC syllabus dotpoints but prelim questions are welcome.

 

[YBK]

o[/sup]C and total pressure of about 250atm is used to optimise the yield of product and time taken. A magnetite catalyst (Fe₃)₄) is used to lower the activation energy, ie reduces the heat required for the reaction, which helps to increase the yield.
Ammonia is used to make fertilisers, household cleaning agents and detergents, as well as plastics and explosives.

hmmm... hsc csu says 525 degrees celsius and 35 000 kPa or 345 atm to give 30 percent yield.. hehe, just studied that dot point!

 

[YBK]

Next Question:
A reagent bottle on a laboratory shelf contains a colourless liquid and has the label:

C₂H₅OH
(95%)

Which of the following is the most important piece of safety equipment when using this substance?

(A) eye protection
(B) a fire blanket
(C) gloves and apron
(D) a fume hood

hmmm i would say eye protection, but then again, it depends on the purpose because you may use it in something that risks causing a fire, in which case a fire blanket would be more important