Stopsign's Chemistry Marathon (2006) (1 Viewer)

[Stopsign]

Hey Chemistry-geeks!
This thread is intended to keep the chemistry-minds of all of you running.

You know how marathons go. (Show working for calculations)

1st question:
Describe advantages and disadvantages of using ethanol as an alternative fuel source.

 

[pLuvia]

Describe advantages and disadvantages of using ethanol as an alternative fuel source.

Advantages

- Renewable
- Cleans the fuel system
- Reduces greenhouse gas emissions
- Cost effective
- Produced by fermentation of sugars and starches or by ethene going through hydration
- Up to 10% of ethanol can be mixed with petrol

Disadvantages

- If the petrol has more than 10% ethanol, engine modifications are required
- Disposal of large amounts of waste after fermentation of sugars and starches
- Large areas needed for the growing of specific crops for the fermentation to ethanol



Next Question:
Describe how transuranic elements are produced, name one that is used in medicine or industry and give a brief description how it is used

 

[Riviet]

Hey not a bad idea! Good for revision. By the way, don't forget to post the next question to keep the marathon going.

 

[pLuvia]

Edited

 

[pLuvia]

Bump? anyone going to answer it?

 

[Dreamerish*~]

Bump? anyone going to answer it?

I would, but there really is no point in that, is there?

Don't worry, bump this up by September and you'll get 50 posts per night.

 

[Cobra]

lol, i reckoned it was a good idea mind you, im not that good at chem

 

[pLuvia]

Bump!

Next Question:
Describe how transuranic elements are produced, name one that is used in medicine or industry and give a brief description how it is used

 

[Kaz Man]

Describe how transuranic elements are produced, name one that is used in medicine or industry and give a brief description how it is used
Transuranic elements are produced in either a nuclear reactor or by cyclotron. In a nuclear reactor, a nucleus of an atom (eg uranium) is lowered between two redioactive plates of uranium and neutrons being emitted by the uranium collide with the nucleus. The heavier atom then emits an electron to stabilise the element. This process produces neutron rich isotopes of elements and is used to produce the first three transuranic elements. A cyclotron is used to produce the remaining elements. Two nuclei of elements are spun together at very high speeds and combine to produce the new element. This process produces proton rich isotopes.
A transuranic element used in industry is Americium 241. This radioactive element is used commerically in smoke detectors. Americium ionises air around it and a circiut is made. when carbon dioxide enters the air around it, the circiut is broken and the alarm is set off. Americium has a half life of about 432 years, which means that it virtually does not need to be replaced in smoke detectors.

I don't know how much of the acidic environment everyone's done but:
Discuss the development of the theory of acids.

I'm not much good at making up questions...

 

[pLuvia]

Discuss the development of the theory of acids.

First definition of acids was a substance having a sour teaste and reacted with certain metals. In 1780, Lavoiser proposed "acids were substances that contained oxygen", which the word oxygen in Greek meant "produces sour taste". This was disproven because bases also contained oxygen and some acids didn't.

In 1815 Davy then suggested: "acids were substances that contained replacable hydrogen".

In 1884, Arrhenius proposed: "acids were substances that ionised in solution to produce hydrogen ions" Acids were strong if they ionised completely and weak if they partly ionised. However this was too vague because ionisation occurs with the solution not the acid by itself.

An acid can react with a base to form a salt, although the acid does not ionise in the solvent

Bronsted-lowry theory of acids and bases was: "An acid is a substance that, in solution, tends to give up protons (hydrogen ions), and a base is a substance that tends to accept protons.

Define Le Chatelier's principle, and factors that can affect equilibrium

 

[.ben]

If a system at equilibrium is disturbed then the thing will minise the effects by shifting the equilibrium?

next question: Using the equation for the haber process, determine the conditions under which the maxium yield of ammonia will be obtained.

 

[aek]

lol, what's the point of this thread? .. to help you with your hw?

 

[Dreamerish*~]

lol, what's the point of this thread? .. to help you with your hw?

To help other people revise, maybe?

If he wanted help with his homework it's completely within his rights to post a thread titled "HELP ME WITH MY HOMEWORK".

 

[Riviet]

Remember that this a Chemical Marathon, not a homework asking thread.

If you need help with homework, you can either post up a new thread or PM someone who can help you out, namely Dreamerish.

 

[richz]

y repeat wat dreamerish just said?

 

[angmor]

time to revive the thread again. im going to answer a question from a long long time ago

next question: Using the equation for the haber process, determine the conditions under which the maxium yield of ammonia will be obtained.

the haber process for the production of ammonia is given by the equation
N₂ + 3H₂ = 2NH₃ H = -1303asomething

according to Le Chatelier's principle, the yield of ammonia can be maximized in regard to this equation in the following ways:
1. increase in pressure - there are more moles of reactant than product, therefore an increase in pressure will disturb the equilibrium, allowing a shift to the right to balance it out. this increases yield of NH₃.
2. removing ammonia as it is formed - by constantly removing the product, the equilibrium is again disturbed and thus more reactant must move across, shifting right, and thus maximizing yield of ammonia.
3. decreasing the temperature - as the reaction is exothermic, and releases excess heat, keeping the temperature low will maximize the product gain.
4. increasing concentration of reactant - either N₂ or H₂.

My question : Describe the difference between an amphiprotic species and an amphoteric species.

 

[bboyelement]

amphiprotic species is one that can act as proton donor and proton acceptor
amphoteric species is one that can act as acid oxide or basic oxide

hope its rite off the top of my head

question from my trial thought it was tricky

a student wished to determine the percentage of calcium carbonate present in a shell found at the beach. the clean dry shell, which weighed 1.306g was placed in a small beaker and 10ml of 5 molar hydrochloric acid was added. when the shell had completely dissolved, with distilled water. A 10ml sample from this solution required 11.2ml of 1 molar sodium hydroxide for complete neutralisation.

a) calculate the number of moles of sodium hydroxide present in the 11.2 ml of 1 molar sodium hydroxide solution.

b)how many moles of acid remained in the beaker after the reaction with the shell?

c)how many moles of acid reacted with the shell?

d)what mass of calcium carbonate was present in the shell?

e) what was the percentage of calcium carbonate in the shell?

if you did this trial then dont ruin it for other ppl please

 

[pLuvia]

I had that exact same question in my trial Worthed like 8 marks

 

[passion89]

I had that exact same question in my trial Worthed like 8 marks

It was in my trial too!!

 

[Riviet]

Just curious but was that 8 marker from this year's independent trial?