Question Chain Thread !!!

[midifile]

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Originally Posted by xiao1985

So what if one gets the question wrong?
Haven't done any real chemistry for 4 years now... hope I can still remmeber:

Lavoisier, Arhhenius [sp], Davy, Bronsted-Lowry, Lewis

Q: How many isotopes could the element with formula C3H8O have, name them.

a. thats not an element, and b. molecules cant have isotopes.

Is the question meant to say, how many isomers does the molecule with the formula C3H8O have?

If so, 2 - propan-1-ol and propan-2-ol

Oh and btw, Davy came before arhhenius

EDIT: Oops, I forgot to ask a new question... qu: Describe the method of the synthesis of a synthetic biopoloymer. Assess the potential of biololymers such as this one for polymers currently produced from petrochmicals.

[squeenie]

I'll do that!

All synthetic polymers are formed by the process of addition polymerisation. Double bonds in the monomers break open to join with other monomers to form a polymer. Examples of synthetic polymers include polyethylene and polystyrene.

I'm assuming that the question was referring to cellulose. Biopolymers such as cellulose have great potential as a partial/complete replacement for polymers made from petrochemicals. Biopolymers are made from renewable resources (such as plant material), and are biodegradable. However, biopolymers are still relatively expensive to produce, and there are still some problems associated with biopolymers. These problems include low resistance to water, and durabilty.

Right. I'm sure I've probably missed a few points and made a few typos. Oh well.

From the 2002 CSSA trial: Discuss the advantages and disadvantages of using models in chemistry. Use examples to illustrate your answer.

[Undermyskin]

Hix.

I choose Polylactide!

Ok, lactic acid can be obtained from milk whey or fermentation process of sugar. The molecules are obligomerized then dimerized to form polylactide with a catalyst being stannous octoate catalyst. (that's basically it)

It has a high potentiality to be used widely as the crude-oil resource diminishes (tho only 3% is used in petrochemical but this alternative can save huge amount of money!). To catch up with the demands for a safe, versatile, biodegradable (environmentally friendly) and sustainable material, polylactide provides a somewhat neutral net CO2 although there are requirements for energy input during fermentation and polymerization processes that need petrol. Its physical properties are similer to those of polystyrene and can be modified to resembles polypropylene's or polyethene's. So it can replace these three popular polymers if not considering the costs!

Other petrol-based polymers contribute to environmental issues and shrinking oil resource. blah blah.

Why do you like to ask so long questions?

Q: What is a model? Assess its advantages and limitations.

Sorry, it's the first question that came up to my mind.

And, isn't it Arrhenius?

What the? I was typing it first!!!!!!!!!

[midifile]

Okay. Im gonna answer both questions in one.

A model is a visual (or other) representation of something that cannot be seen in real life, due to being too small, too big, take to long to occur, or occur to quickly. Models can be used to represent these things so they can be seen and studied.

Advantages: Allows us to be able to study something that would normally be unable to study. Also, some models are working models, allowing use to see its function (ie Esterification and polymerisation can be modelled using molymods, and the bond breaking and reforming processes can be seen).

Disadvantages: Models often oversimply things and reduce a lot of the required detail of concepts. Models are usually not to scale (ie with molymods you can not see the relative size of particles).

Question: Evaluate the use of sodium hydroxide as a primary standard

[twilight1412]

im pretty sure its because its anhydrous its crap
it absorbs water from the surrounding environment and it adds to the weight throwing off your calculations
if im right feel free to post another
if im wrong someone else answer it :P

[minijumbuk]

Originally Posted by midifile

Question: Evaluate the use of sodium hydroxide as a primary standard

It's a shit one to use because it's deliquescent.

Undermyskin, I challenge you:
If you have a pH 3 acetic acid solution and a pH 3 HCl solution, predict which one will require more alkaline solution to neutralise it in a titration.

[squeenie]

I'm going to make an attempt to bring this thread back to life (and its probably going to be an epic failure)

From the 2005 HSC: Analyse how knowledge of the composition and properties of acids has led to changes in the definition of acids. (5 marks)

Go for it!!

[adnan91]

Originally Posted by squeenie

I'm going to make an attempt to bring this thread back to life (and its probably going to be an epic failure)

From the 2005 HSC: Analyse how knowledge of the composition and properties of acids has led to changes in the definition of acids. (5 marks)

Go for it!!

LDAB laviosir->davy->arhenuis->bronsted

[SkimDawg]

Originally Posted by adnan91

LDAB laviosir->davy->arhenuis->bronsted

What a pro attempt..

Early definitions of acids were based on their properties, including their effect on indicators and their reactions with other substances. Acidic substances such as vinegar and lemon juice were known to taste sour and react with bases. In the 17th century, Robert Boyle sed this knowledge of properties to define acids as all sour-tasting substances.
Most acids such as CH3COOH, H2SO4, and H2CO3 were known to contain oxygen and this was ued by Antoine Lavoisier as the basis of his definition in 1779. He thought that all oxides dissolved in water to form acids.

However, many oxygen-containing substances have since been found to be basic, such as sodium oxide and calcium oxide. Also, some acidic substances were known not to contain oxygen, such as HCL and HCN. Acids were shown to react with metals forming salts, e.g ZnCl2. Humphry Davy, in the early 1800s, used these observations to define acids such as substances that contain replaceable hydrogen.

In 1884, Svante Arrhenius proposed a theory to explain the properties of acids that were known by at that time. Acids were known to conduct electricity and react with metals to produce hydrogen gas. These observations suggested that ions were involved. Arrhenius defined acids as substances that ionise in solution to produce hydrogen ions. Strong acids ionise fully and weak acids slightly.

Arrhenius defined bases as substances that produce hydroxide ion in water but carbonates were shown to be basic without hydroxide, Because this current theory had inconsistencies like this, Johannes Bronsted and Thomas Lowry in 1923 redefined acids as proton donors and bases as proton acceptors. They elaborated to say that acids give up protons to form conjugate bases and that a strong acid will form a weak conjugate base. They came to this conclusion by observing that the solvent seemed to play a role in acid behaviour. The strength of an acid appeared to be due to the nature of the solvent. They also observed that different salts had different pH's.

[SkimDawg]

Yeah I forgot the next qu lol.

2006 HSC Q24b) Evaluate the significance of Haber’s discovery at that time in world history. (4 marks)

[liamh16]

Haber's discovery of the production of ammonia prolonged the Second World War, thus, has a. Haber discovered that ammonia can be produced from its component elements;Nitrogen gas and Hydrogen Gas, to produced NH3;
N2(g) + 3H2(g) <--> 2NH3(g)
This discovery allowed the German Military to develop Chlorine and Mustard Gases, which were heavier than air and would be dropped into the trenches, burning and killing the Soliders they contained.
Ammonia is also used in the production of explosives, and these two factors lead to the deaths of many soldiers in the second world war. If Haber had not discovered the process, many lives would have been spared, and the war would not have been prolonged. Therefore, when Haber discovered the process for the production of ammonia, now known as the Haber Process, it has an extremley large singificance in that time period, due to the enormous amount of soliders killed.



( i think that was evaluated well enough )



Next Question:

Assess the accuracy of information you used to identify the steps taken to alleviate the ozone hole problem and use of CFC's.

[JasonNg1025]

Ok, here we go.

From your post, liamh16, ammonia is also used in fertilisers which was crucial at that point as Germany also used to ship them, but could not. If not for Haber, they would've been out of food.

Gosh, I have never seen your question, nor have I seen it in the Syllabus. Is it a question in one of the HSC papers?

[liamh16]

Ooooh yeah the food! Riiiight.
Well the question is one my teacher gave us that are challenging questions that are from the syllabus but are skills based. The dot point in the syllabus is 'Analyse the information available that indicates changes in atmospheric oxone concentrations, describe the changes observed, and explain how the information was obtained.' I think.
Just quietly, why are you doing this if your doing your HSC in 2010? Are you super accelerated or something?
I'll give everyone a different question, then.
Ummm;
Explain why monitoring the reaction vessel in the Haber process is crucial and describe how this is done.

[insomniac90]

Originally Posted by liamh16

Explain why monitoring the reaction vessel in the Haber process is crucial and describe how this is done.

Monitoring the Haber process is important to create maximum yield as well as for safety. Conditions in reaction vessel are of a compromised temperature of 200C and pressure of 100kPa. According to LeChatelier, the decrease in temperature slows the rate of reaction as the reaction is endothermic.

Ammonia is liquefied and removed to increase yeild as the absence of 2NH3 will shift the equilibrium to the right.

The production of excess carbon monoxide also must be removed as this destroys the catalyst.

And that's all I can think of right now =/

Q. WHAT IS THE DIFFERENCE BETWEEN AMPHITERIC AND AMPHIPROTIC?

[liamh16]

Originally Posted by insomniac90

Monitoring the Haber process is important to create maximum yield as well as for safety. Conditions in reaction vessel are of a compromised temperature of 200C and pressure of 100kPa. According to LeChatelier, the decrease in temperature slows the rate of reaction as the reaction is endothermic.

Ammonia is liquefied and removed to increase yeild as the absence of 2NH3 will shift the equilibrium to the right.

The production of excess carbon monoxide also must be removed as this destroys the catalyst.

And that's all I can think of right now =/

Q. WHAT IS THE DIFFERENCE BETWEEN AMPHITERIC AND AMPHIPROTIC?

The Haber process is an exothermic reaction....