Question Chain Thread !!! (2 Viewers)

[danz90]

I have

2NH₄⁺ + 2e^- --> 2NH₃ + H₂

2MnO₂ + H₂ --> Mn₂O₃ + H₂O

And so

2MnO₂ + 2NH₄⁺ + 2e^- --> 2NH₃ + Mn₂O₃ + H₂O

Hmm they look different...

I spoke to the HSC advice line about this...

She said that they are both essentially correct, and would not be marked wrong, its just that mine goes an extra stop to show the resulting base when the oxide of manganese dissolves in the water present in the electrolyte paste.

Just stick with what you've been doing all year

 

[JasonNg1025]

Rawr danz90 beatcha to membrane filter

1-bromo-1-chloro-2,2,2-trifluoroethane? I'm not good at naming ><

EDIT : Oh noes would it be

2-bromo-2-chloro-1,1,1-trifluoroethane?
Cause the sum is smaller

Ok looks like I was wrong then

 

[Azreil]

Eeek.

Um. Smallest numbers, smallest numbers.

2-bromo-2-chloro-1,1,1-trifluoroethane.

Evaluate the effectiveness of replacements for CFCs

EDIT: See, this is why naming things sucks. I can't remember if it's smallest numbers or alphabetical.

 

[danz90]

Rawr danz90 beatcha to membrane filter

took me a few minutes to find a nice diagram of a haloalkane lol

 

[danz90]

Eeek.

Um. Smallest numbers, smallest numbers.

2-bromo-2-chloro-1,1,1-trifluoroethane.

Evaluate the effectiveness of replacements for CFCs

EDIT: See, this is why naming things sucks. I can't remember if it's smallest numbers or alphabetical.

That's correct, because you've got to have the lowest number for the atom/halogen thats most abundant.
Or you can just use plain logic to try and get the smallest numbers possible in your name.

arrange them by alphabetical, like you have.

bromo --> chloro ---> fluoro ---> iodo

 

[JasonNg1025]

Replacement for CFCs include HCFCs (hydrochlorofluorocarbons) and HFCs (hydrofluorocarbons).

HCFCs have alleviated the CFC ozone depletion problem due to the unstable C-H bond. This allows it to decompose in the troposphere without even reaching the stratosphere to harm it. However, some molecules have escaped into the stratosphere, and have depleted thousands of ozone molecules.

HFCs have fully resolved the further ozone depletion problem. This is because they also have the C-H bond which lets most of the molecules decompose in the troposphere. Also, it does not contain bromine or chlorine, so even if it leaks into the stratosphere it cannot destroy ozone.

Therefore, replacements for CFCs have been effective in solving the ozone problem. Unfortunately, CFCs already in the stratosphere will continue to deplete ozone until the Cl reacts with another chemical to form a stable substance.

 

[JasonNg1025]

took me a few minutes to find a nice diagram of a haloalkane lol

Yaa I gotta practise more haloalkane
Me gonna give youse one

 

[danz90]

Describe the use of the above apparatus in volumetric analysis.

 

[JasonNg1025]

This piece of glass is a volumetric flask. It is useful in volumetric analysis as you can measure out accurate quantities of liquids (using the graduation mark) to create standard solutions of a desired substance. The stopper allows the substance (presumably solid) and water to be shaken up to allow for better dissolving.

Gosh, where do you get these questions?

 

[Azreil]

...Hmm. Let's try this.

The above is a round bottomed flask. This is a very precise measuring device used in titrations to prepare primary standards. A precisely measured weight of a suitable primary standard (such as oxalic acid) is placed in the flask and an amount of distilled water added. The top of the flask is placed in it and the flask is inverted several times. Further distilled water is then added by way of a wash bottle so the bottom of the miscus is even with the line marked on the neck of the flask. The molarity of the primary standard can now be calculated with great accuracy and hence can be titrated against to find the molarity of a secondary standard.

Is that what you wanted? xD

Describe the method you would use to determine a Cl- ion was part of a solution.

 

[danz90]

This piece of glass is a volumetric flask. It is useful in volumetric analysis as you can measure out accurate quantities of liquids (using the graduation mark) to create standard solutions of a desired substance. The stopper allows the substance (presumably solid) and water to be shaken up to allow for better dissolving.

Gosh, where do you get these questions?

lol I just make them up. It's better to have questions with diagrams/calculations in this thread that don't involve very long responses, otherwise who can be f'ed to write long responses.

Next:

What should the above apparatus be rinsed with, in preparing for a titration, AND WHY?​

 

[Azreil]

This should be rinsed with the aliquot -- that is, the liquid it will be used to measure. This is because if it was rinsed with water the molarity of the aliquot would be altered and hence the method would be invalid.

How many isomers are there of C2H3Cl2F? Name them.

 

[JasonNg1025]

Your first question - to test for Cl^-, you add AgNO₃ and watch carefully for a precipitate.

Second question, 3?

1,1-chloro-1-fluoroethane

1,1-chloro-2-fluoroethane

1,2-chloro-1-fluoroethane

I'm probably wrong again

 

[danz90]

This should be rinsed with the aliquot -- that is, the liquid it will be used to measure. This is because if it was rinsed with water the molarity of the aliquot would be altered and hence the method would be invalid.

How many isomers are there of C2H3Cl2F? Name them.

I've counted four (although most likely wrong).

1,1-dichloro-1-fluoroethane
1,1-dichloro-2-fluoroethane
1,2-dichloro-1-fluoroethane
1,2-dichloro-2-fluoroethane

?

 

[JasonNg1025]

OOH PICK ME

For 1,2-dichloro-2-fluoroethane, wouldn't that rather be 1,2-dicholoro-1-fluoroethane because you count from the other end?

 

[hoochiscrazy]

With the solubility rules and exceptions, what topic and part of the syllabus is it? Any help would be great thx.

 

[Azreil]

Yeah, these are the same:
1,2-dichloro-1-fluoroethane
1,2-dichloro-2-fluoroethane

There are 3 :]

Explain the issues with Arrhenius' definition of acids

 

[JasonNg1025]

Everywhere? It's general knowledge, great to know it some random situations

EDIT: I actually remember doing it in year 11

 

[Azreil]

With the solubility rules and exceptions, what topic and part of the syllabus is it? Any help would be great thx.

Chemical Monitoring & Management:
Part 3 dot point 1:
deduce the ions present in a sample from the results of tests

 

[SkimDawg]

Explain the issues with Arrhenius' definition of acids

Arrhenius; stated that ACIDS produced H+ IONS when in WATER.
He proposed the idea that acids disassociate into their ions when they are dissolved in water. Thus, he hypothesised that acids release a H+ when in an aqueous solution. He also said that bases release OH־ ions in aqueous solutions. Because it had inconsistencies, it was later improved by Bronsted / Lowry, as proton donors and acceptors, blah blah..