Question Chain Thread !!! (2 Viewers)

[minijumbuk]

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]

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]

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]

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]

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....

 

[insomniac90]

The Haber process is an exothermic reaction....

hahah i knew it. cbb to look it up though.
thanks for correcting me. =]

 

[j-3-s-5]

Q. WHAT IS THE DIFFERENCE BETWEEN AMPHITERIC AND AMPHIPROTIC?

An amphiprotic substance is a substance that can act as both a proton donor and as a proton acceptor. (related to Brosnted-Lowry acid-base definitions)

An ampthoteric substance can react as an acid or a base according to the Arrhenius definitions (when dissolved in water an acid increases concentration of hydrogen ions, and a base increases the concentration of hydroxide ions)

They are are so damn similar its confusing lol. Although my understanding of acids and bases is very amatuer lol.

Q. Explain the formation of acid rain. (Including equations)

 

[JasonNg1025]

Well since it's the formation on Acid Rain, I won't blab about the original sources of stuff.
Basically, acid rain is formed when sulfur dioxide and oxides of nitrogen are emitted into the atmosphere... they see a cloud and dissolve in it. Firstly, for sulfur dioxide:

SO_{2 (g)} + H₂O _(l) --> H₂SO_{3 (aq)}

...which is sulfurous acid. Also, SO₂ turns into SO₃ with other air impurities acting as the catalyst.

2SO_{2 (g)} + O_{2 (g)} --> 2SO_{3 (g)}

... and this dissolves in water to form the well known sulfuric acid.

SO_{3 (g)} + H₂O _(l) --> H₂SO₄

For the oxides of nitrogen... firstly, say we start from NO.

2NO_(g) + O_{2 (g)} --> 2NO_{2 (g)}

Now this one... I'm not too sure. But what I learnt was:

4NO_{2 (g)} + 2H₂O _(l) + O_{2 (g)} --> 4HNO_{3 (aq)}

And stufffff like that. I may be wrong for some equations, we'll need another opinion.

Question: How are radioisotopes and transuranic elements produced? (I know a little, it's just that... in my knowledge they're a bit too similar.)

EDIT: Ow, I hate typing SUB and /SUB now

 

[minijumbuk]

Jason, you hate sub /sub?
Look at this thread.
http://community.boredofstudies.org/showthread.php?p=3870425

Took me millions of years to subscript the n's and the 3's and the 2's xD
PS: Are you really 13?

Anyways...

First 3 transuranic elements produced in nuclear reactors by neutron bombardment which causes beta decay, forming an element with 1 more proton than before, thus forming a new element.
The rest are made by bombarding a small atom such as carbon into the nucleus of the uranium. The atomic numbers add up, and a new transuranic element is formed.
This is done in a cyclotron or linear accelerator.

Normal radioisotopes are also produced in nuclear reactors by neutron bombardment.

 

[JasonNg1025]

Ok, thanks ;D

Err, I saw your post. I thought you found a way out using copy and paste
But it's a little different for me
And yes, I turned 13 last saturday

 

[I-Love-Jesus]

Wowwwww... You did Ext. 1 & 2 Maths when you had just turned 12? That's impressive!
How did you go? I must say though, I would've rathered last years exams to this years!

Anywho, you can choose between the following two questions:

"Analyse the relationship between the position of elements in the Periodic Table, and
the acid–base behaviour of their oxides."

and

"The flow chart shows a series of steps involved in the production of ethyl butanoate.

glucose → mixture containing ethanol → pure ethanol → ethyl butanoate

Describe the chemistry and procedure involved in each of these steps, using diagrams
where appropriate."

That last one was a 7 mark question, but that requires a lot of writing, so just a brief overview will do. I've just never been able to remember that for some reason. =[ And the first one's been giving me strife as well.

 

[j-3-s-5]

"Analyse the relationship between the position of elements in the Periodic Table, and
the acid–base behaviour of their oxides."

- Metal oxides are mostly basic
- Non metal oxides are mostly acidic.
- Oxides of the 5 elements close to the borderline between metals and non-metals are amphoteric, that is, they show acid and basic properties.

Yeh kinda simple answer but thats all I could come up with lol.

Describe the design and composition of microscopic membrane filters and explain how they purify water.

 

[minijumbuk]

Ok, thanks ;D

Err, I saw your post. I thought you found a way out using copy and paste
But it's a little different for me
And yes, I turned 13 last saturday

Wow, you're a prodigy =OOOOO

IQ.....~130?

 

[SkimDawg]

Microscopic membrane filters can be used to remove fine particles and micro-organisms from water that cannot be removed by the normal treatment.
Membrane filters are made of thin polymer sheets with fixed pore sizes. The commonly used polymers are PVC, polycarbonate, polypropylene, polyester and polysulfone. The polymer sheets are folded or wound around a central, rigid core to form a cartridge that can be replaced as required. Other microfiltration membranes consist of fine hollow capillaries that are housed inside a filtering unit. Here the filtered particles are trapped on the outside of the capillaries and the filtrate passes through the centre of the capillary. Water that is to be filtered is made to flow across the surface of the membranes rather than at right angles to prevent clogging.

The filters can be cleaned by back-flushing. Air is blown from the clean side to dislodge trapped particles which are then washed away by the dirty water on the outside.

Membrane filters are widely used for filtering both drinking water and treated sewage. For drinking water, membrane filters can remove virtually all particles larger than 0.2 nanometres including Giardia and Cryptosporidium. Primary and secondary sewage treatment removes about 90% of BOD and 90% of suspended solids from raw sewage. Membrane filtration is widely used in industry, particularly for beverage preparation (including bottled water).

However, no filters can remove substances that are actually dissolved in the water such as phosphates and nitrates and heavy metal ions.

Copied from other thread lol, now next qu

There are many benefits and problems associated with the use of radioisotopes in industry and medicine. Evaluate the impact on society of the use of radioisotopes in both industry and medicine. In your answer, give examples of specific radioisotopes, making reference to their chemical properties. (7 marks).

 

[danz90]

[-- Official 2008 HSC Chemistry Pre-exam Study Thread --]

Well, the other chain thread doesn't seem to be going good.
Let's make this the official study thread.

You know the drill... answer a question - give a question.

Ok, lets begin:

Explain why monitoring of the reaction vessel used in the Haber process is crucial and discuss the monitoring required.