Chemistry Marathon 2007 (1 Viewer)

[wrxsti]

i saw a thread like this in the "business studies" section so i thought i wud try one here
"students have found it a great way to quiz each other on various areas of the syllabus and share their knowledge"

How To Play
The first person asks a Chemistry question. The next person answers it then posts another question for the next person then so on.

Ill begin

1) Why is the PH of HCl (Hydrochloric Acid) vastly lower than that of CH3COOH (acetic acid)

 

[wrxsti]

Question:

5 Marks

Analyse how knowledge of the composition and properties of acids has led to changes in the definition of acids.

k, we'll try to put up past questions.


Antoine Lavioser, A french chemist. first proposed that acids were made up of 2 substances, one of which was oxygen, he further went on to claim that All acids contained Oxygen. This was the first known Definition of an Acid.
Substances classified: CH3COOH., H2SO4

Humphry Davy, an english chemist proved Hydrochloric Acid, contained hydrogen and Chloride and no oxygen, He also noticed numerous acids contained replaceable hydrogen, he went on to state all Acids contained Hydrogen
Substances Classified: HCl

Svante Arrhenius, A swedish chemisty whose work was based on theory, (no experiments) he suggested acids and bases were neutral substances which dissolved to give H+ and OH-
Limitations: his definition only considers acidic and basic substances,
Does not consider Amphiprotic
Must be Aqueous

Bronsted Lowry: Theory involving proton Donation whereby an acid is a proton donor and a base a proton accepter

Question 3) the hydrogen Carbonate Ion can react in the following ways
HCO3- + H20 -> OH- + H2CO3
HCO3- + H20 -> H30+ +CO32-

How would you know which reaction was being favoured?

 

[wrxsti]

just coz this is an issue my teacher brings up a lot, even though ppl think that Sir humphry davy came up with the notion of replaceable hydrogen it was infact Von Liebig some rich Count that came up with the idea.

oh ok

 

[ssejamafone]

just coz this is an issue my teacher brings up a lot, even though ppl think that Sir humphry davy came up with the notion of replaceable hydrogen it was infact Von Liebig some rich Count that came up with the idea.

other than that solid answer

soo... does that mean we'd lose marks for putting 'Davy' instead of 'Liebig'?

 

[wrxsti]

soo... does that mean we'd lose marks for putting 'Davy' instead of 'Liebig'?

Dont think you will

 

[ssejamafone]

nah accordin to my teach its fine to put davy and mention von liebig on the side, even though my teacher sends them(BOS) emails statin to change it.

oh, ok... phew...

although, our teacher has never mentioned Liebig at all during class.....

 

[wrxsti]

oh, ok... phew...

although, our teacher has never mentioned Liebig at all during class.....

yeah same.
BACK TO THE QUESTION lol

 

[timb89]

leibg isnt in the syllabus only davy, arhenius, lavoiser and lowry-bronsted. look at the dot points. surely we dont need to know anything bout him other wise it would state it in the sylabus. please excuse spelling.

 

[Steth0scope]

Answer: Add the HCO3 to a neutral solution such as water. Stick a pre-calibrated pH probe in there with a data logger connected on the side. A pH of >7 indicates the favoured equation is the one that favours the formation of OH- ions. A pH of <7 indicates the favoured equation is the one that enhances the formation of H3O+ ions.

Next question:
Am i gay?
Answer: YES!

Next question:
Describe the process of eutrophication, and assess the suitability of water quality tests used to monitor it.

 

[locksophalanga]

Next question:
Describe the process of eutrophication, and assess the suitability of water quality tests used to monitor it.

is eutrophication in the chemistry syllabus as well as biology?

 

[ssejamafone]

is eutrophication in the chemistry syllabus as well as biology?

Well, it's not stated specifically in the dot points, but you should know about it, and how it is caused, etc.

edit: I WAS WRONG. it IS in the syllabus, so you DO need to know about it.

 

[yoakim]

Eutrophication is a natural process where water bodies receive excess nutrients that stimulate excessive plant growth - eg discharge of nutrients, such as phosphates and nitrates.​

Algal bloom is associated with it which is the excessive growth of algae or other aquatic organisms in a waterway. These occur when there are high concentrations of these nutrients. Phosphates are naturally only available in low concentrations, so when it becomes readily available plant growth increases rapidly. Organisms that can causing algal blooms include green algae and cyanobacteria (blue-green algae).

There are detrimental effects of eutrophication such as making water unsuitable for stock, aquatic life and humans and often leading to seasonal deficiencies in dissolved oxygen - some of which are caused by the release of toxins by bacteria into the waterways.

Ahhhh, I can't be bothered answering the second part of the question, but basically: The water quality tests used to monitor it are fairly effective. A range of tests used simultaneously or in conjunction with others enhances the quality, eg: BOD/DO tests and N (10:1) tests. Ultimately they allow the monitoring of the rate of eutrophication in the specific water bodies which allows the monitoring of future outbursts of it, hence acheiving the ultimate purpose of protecting the environment. Dah di dah di dah...

Alright, now for my question...This was a surprising question in the 2007 NEAP paper. Forced me to review ppm and all those conversion of units...

The concentration of carbon dioxide (C02) in the troposphere over Dubbo is measured to be 1.28 x 10 POWER OF -5 mol/L.
Assuming conditions of 25*C and 100kPa, what is this concentration in parts per million (ppm)? Show all working.

 

[locksophalanga]

Well, it's not stated specifically in the dot points, but you should know about it, and how it is caused, etc.

edit: I WAS WRONG. it IS in the syllabus, so you DO need to know about it.

which dot point? specifically?

 

[ssejamafone]

which dot point? specifically?

Chemical Monitoring and Management:

Dot Point 5 - in the right hand column

students: gather, process and present information on the range and chemistry of the tests used to:
- identify heavy metal pollution of water.
- monitor possible eutrophication of waterways.

 

[Martyno1]

I have no idea if this is correct but is it 12.8 ppm?
(1.28 × 10^-5)moles / 1L = y ppm / 10⁶ L

y ppm = 10⁶(1.28 × 10^-5)
y = 12.8
12.8 ppm

I might have got that completely incorrect because it sounds too easy.

Next question: State the 5 conditions necessary for fermentation to occur and describe why each one is necessary.

 

[yoakim]

Sorry martyno1, but that's incorrect. I'll answer your question though. The 5 conditions are:
1. Source of a micro-organism which is alcohol-tolerant eg:Yeast. Yeast can undergo anaerobic respiration to form CO2, which is an indication (with its reaction with Ca(OH)2) of the formation of ethanol from glucose.
2. Nutrients for the yeast to function...
3. No oxygen - (sealed container) - yeast is anaerobic...
4. Warm temperatures of 32-38*C - range in which the yeast's enzyme function optimally for respiration.
5. Glucose - part of the respiration process...


Next question: A student determined in the laboratory that the % by mass of water in CuSO4.5H2O is 40.0%. If the accepted value is 36.0%, what is the Percent of error?
a) 0.11%
b) 1.1%
c) 11%
d) 4.0%

 

[Martyno1]

Sorry martyno1, but that's incorrect. I'll answer your question though. The 5 conditions are:
1. Source of a micro-organism which is alcohol-tolerant eg:Yeast. Yeast can undergo anaerobic respiration to form CO2, which is an indication (with its reaction with Ca(OH)2) of the formation of ethanol from glucose.
2. Nutrients for the yeast to function...
3. No oxygen - (sealed container) - yeast is anaerobic...
4. Warm temperatures of 32-38*C - range in which the yeast's enzyme function optimally for respiration.
5. Glucose - part of the respiration process...

5 is glucose should be in an aq solution

and I think I got the answer to the one you posted above.. would it be 0.457 ppm, is that correct? If not I have absolutely no idea.

 

[wrxsti]

0.5632 ppm ???? for the CO2 Question

 

[wrxsti]

0.5632 ppm ???? for the CO2 Question

im pretty sure thats right :S .... i think..... gosh i need NEAP papers

Next Question

Describe how commercial radioisotopes AND transuranic elements are produced.... (5marks)

 

[Martyno1]

How did you do that? I am so lost.