Question Chain Thread !!! (1 Viewer)

[@who]

Describe the roles of a certain chemist, and explain some methods which they use in their occupation.

Dr.Ian Russell of the CSIRO.
Role:
- assessment of aust. wool quality for purpose of export.
- he assesses the degree of impurities within the wool
methods:
-Uses principals of AAS to detect concentrations of impurities
- then relies on collaboration with organic chemists for type of impurities
- He also undertakes analytic chemistry in his career as he calculate + molar composition of impurities contained within the wool.

 

[imqt]

Buhan Gemikonakli
role: analytical chemist...he monitors the transfromation of ethane into ethene, analyses waste water to rid it of any dangerous impurities, and collaborates with other chemists eg environmental chemist

Uses GAS CHROMOTOGRAPHY --which involves a sample being vapourised into a stream of helium that is passed through a solid or liquid coated solid

 

[imqt]

Compare The Properties Of Gaseous Forms Of Oxygen And The Oxygen Free Radical

 

[danz90]

I think we miscommunicated here. It's why I asked you to define 'neutralization'.

To be concise and precise, it's the complete reaction between H+ and OH-.

The misconception met with titration is that it's not always a neutralization when referring to a pH of 7.

When you neutralize a acid with a base, the fundamental thing is their products are: salt and water, nothing else. And remember: NEUTRALIZATION GOES TO COMPLETION!!!

So, as I reminded you before, ionization of weak acid is an equilibrium and as long as you add NaOH, this pushes the reaction to the direction whose end result contains merely two primary products: salt and water.

You've probably got confused with the action of CH3COO- and the fact the end point lies well to the alkaline part. Who says that when dissolving CH3COONa into water, it doesn't give basic pH? Even tho the neutralization goes to completion, CH3COO- present still acts as a base. The salt formed can be basic, acidic or neutral, remember?

So it's perfectly manifest that the end point is around 8-9 as you say while all H+ is consumed to produce H2O.

OMG. Not another chemist! I've got none ...er... haven't decided yet actually.

lol I even forgot what the hell we were talking about.

Btw, guys I think that the syllabus doesn't say you need to know a particular scientist (ie with name and all), know a type of chemist, that works in a NAMED industry, and what chemical properties they use etc.

 

[zxcvbee]

Compare The Properties Of Gaseous Forms Of Oxygen And The Oxygen Free Radical

Oxygen molecule
*very Stable
*Electrons are paired
*Colourless/odouless
*bp -183
*essential-required by living organisms for respiritation
*Used medically for breathing difficulties
*pop test

Ozone
*Highly unstable
*colourless/ Strong smell
*bp -111
*Poisnous
*Oxidising agent, sterliation (pools)
*Odour, ir spectrometry

Oxygen radical
*Very unstable/highly reactive
*Produced by the decompostion of O2 by UV light
O2 + UV--> O. + O.
* one or more lone or unpaired electrons

I dont know what else to say about this..


My questions are...

1) State the fermentaion equation and the conditions under which fermentaion occurs.

2) Why is only 15% alcohol concertration possible...

 

[JasonNg1025]

1) C<SUB>6</SUB>H<SUB>12</SUB>O<SUB>6 (aq)</SUB> ---------------> 2C<SUB>2</SUB>H<SUB>5</SUB>OH<SUB> (aq)</SUB> + 2CO<SUB>2 (g)</SUB>

In the above equation, you have to put yeast above the arrow.
Fermentation occurs at around 37<SUP>o</SUP>C (body temperature) with yeast. Different temperatures are infavourable for the yeast and can kill it. Ensure that there is very little or no oxygen in the reaction area. Sterilise equipment (of course...)

 

[zxcvbee]

Another neutralisation q:

pH of solution when 10ml of 0.02 mol/L sulfuric acid is mixed with 13ml of 0.12 mol/L NaOH

i feel like doing this..

H2SO4 + NaOH--> H2O + Na2SO4

10 ml 13mL, 0.12 molar Moles= 0.12 x 0.013
0.02 molar = 0.00156

Moles= c x L
= 0.02 x 0.01
= 0.0002

Therefore; all H2SO4 is used up, and NaOH isnt (strong base, NaOH--> Na+ + OH-)
ie 0.00156-0.0002
=0.00136

Therefore
[H+] = 10^-14/ [OH-]
= 10^-14/ 0.00136
= 7.35 x 10^-12

Therefore pH= -log1o [H+]
= 11.1

 

[zxcvbee]

1) C<SUB>6</SUB>H<SUB>12</SUB>O<SUB>6 (aq)</SUB> ---------------> 2C<SUB>2</SUB>H<SUB>5</SUB>OH<SUB> (aq)</SUB> + 2CO<SUB>2 (g)</SUB>

In the above equation, you have to put yeast above the arrow.
Fermentation occurs at around 37<SUP>o</SUP>C (body temperature) with yeast. Different temperatures are infavourable for the yeast and can kill it. Ensure that there is very little or no oxygen in the reaction area. Sterilise equipment (of course...)

heyy you forgot to answer the the 2nd part!
Your other answer is right but i think you would be better off saying "higher" temperatures are infavouable as it will kill the yeast, not different, as fermentation can occur between 25-37 degrees.

Oh and post a question! lol

 

[imqt]

Discuss How Atmospheric Ozone Concentration Is Measured?

 

[imqt]

Oxygen molecule
*very Stable
*Electrons are paired
*Colourless/odouless
*bp -183
*essential-required by living organisms for respiritation
*Used medically for breathing difficulties
*pop test

Ozone
*Highly unstable
*colourless/ Strong smell
*bp -111
*Poisnous
*Oxidising agent, sterliation (pools)
*Odour, ir spectrometry

Oxygen radical
*Very unstable/highly reactive
*Produced by the decompostion of O2 by UV light
O2 + UV--> O. + O.
* one or more lone or unpaired electrons

I dont know what else to say about this..


My questions are...

1) State the fermentaion equation and the conditions under which fermentaion occurs.

2) Why is only 15% alcohol concertration possible...

to the second question

because yeast cannot tolerate more than 15% alchohol because the zymase enzyme would be damaged

 

[zxcvbee]

to the second question

because yeast cannot tolerate more than 15% alchohol because the zymase enzyme would be damaged

hehe thanks ! i wass really excited about that question lol

 

[imqt]

hehe thanks ! i wass really excited about that question lol

np have a go at my question please

 

[JasonNg1025]

H2SO4 + NaOH--> H2O + Na2SO4

Imbalanced equation?

2NaOH _(aq) + H₂SO_{4 (aq)} ---> Na₂SO_{4 (aq)} + 2H₂O _(l)

Mol H₂SO₄ = 2 x 10^-4

Mol NaOH = 1.56 x 10^-3

4 x 10^-4 mol NaOH reacted

==> 1.16 x 10^-3 mol left

Mol OH^- = 1.16 x 10^-3
This is in 23mL of stuff

[OH^-] = 0.05 mol L^-1

pOH = 1.30
==> pH = 12.7

I've always been kinda weak in this area, so I'm probably wrong

 

[JasonNg1025]

np have a go at my question please

Gaseous oxygen:

- Relatively stable
- Required for life
- Will not react in atmosphere unless acted upon by UV rays

O ^2-:

- Much more toxic
- Will react with surroundings

 

[imqt]

not that question

this one

Discuss How Atmospheric Ozone Concentration Is Measured?

 

[zxcvbee]

Imbalanced equation?

2NaOH _(aq) + H₂SO_{4 (aq)} ---> Na₂SO_{4 (aq)} + 2H₂O _(l)

Mol H₂SO₄ = 2 x 10^-4

Mol NaOH = 1.56 x 10^-3

4 x 10^-4 mol NaOH reacted

==> 1.16 x 10^-3 mol left

Mol OH^- = 1.16 x 10^-3
This is in 23mL of stuff

[OH^-] = 0.05 mol L^-1

pOH = 1.30
==> pH = 12.7

I've always been kinda weak in this area, so I'm probably wrong

ohh sorry your TOTALLY right it was unbalanced and i forgot to do the whole '23ml' thing
thanks!

 

[midifile]

not that question

this one

Discuss How Atmospheric Ozone Concentration Is Measured?

- Ground based dobson spectometers at Halley Bay Antarctica - They are pointed vertically upward and measue the light intensity of frequencies that ozone absorbs (ie UVA and UVC) and intensity of frequencies above and below this range (that ozone does not absorb). By comparing the intensities they can calculate the difference in absorption to calculate the concentration of ozone at that area
- UV lasers - ground based lasers are pointed vertical and fire pulses UV light of different wavelength, and the absorption is calculated at various levels by UV spectroscopes attached to satellites
- TOMS (total ozone mapping stratosphere) - put on satellites and measure ozone concentration at different altitutudes and geographical locations

 

[zxcvbee]

not that question

this one

Discuss How Atmospheric Ozone Concentration Is Measured?

ozone can be measured by
*ground based dobson spectrophotometer, which measures the intensity of light reaching the surface & comparing this to the UV frequencey known not to be absorbed by ozone. (dobson units)

*Instruments on high altitude ballons, which carry instuments into the stratoshere to measures concentrations as a function of altitude

* TOMS total ozone mapping spect. carried by satelites in orbit- produces contour maps


** Name the differences between an oxygen free radical and an oxygen atom

 

[aussiechick007]

** Name the differences between an oxygen free radical and an oxygen atom

oxygen free radical:
- is unstable, has a very short existence, mp and bp unknown.
- has 6 valence electrons in its outer shell, 2 of which are unpaired.

oxygen atom:
- colourless, bp of -183oC.
- is stable, has a low solubility in water.
- consists of 2 oxygen free radicals with their unpaired electrons in a covalent bond.

Evaluate the significance of Haber's discovery of a method of synthesising Ammonia at that time in world history.

 

[yorkstanham]

Evaluate the significance of Haber's discovery of a method of synthesising Ammonia at that time in world history.

Fritz Haber’s discovery of a method to synthesise ammonia was extremely significant at that time in world history. It was during WWI that the British blockaded the German’s supply of nitrates from South America. This had devastating effects on Germany’s ammunition and crops. Haber’s process allowed Germany to produce up to 200 tonnes of ammonia a day, this allowed for fertilisers to be created which boosted crops and hence food for Germany and its troops, the ammonia was also used to create ammunition. Some historians say that the Haber process allowed Germany to prolong its time in the war by 2 years, significantly changing the course of history during the early 20<SUP>th</SUP> century.

NEXT Q:
The atmosphere contains acidic oxides of sulphur which have been increasing in concentration since the Industrial Revolution.<?xml:namespace prefix = o ns = "urn:schemas-microsoft-comfficeffice" /><o></o>
Discuss the evidence for this statement, and include relevant balanced chemical equations. (4 marks)<o></o>