How did it go ? CSSA trial (2 Viewers)

[littlemic21]

does any one have the RIGHT answer to that wine q???
like evry 1 else i just bulled it!

 

[Ragerunner]

I'm pretty sure im right. you have to look at both equations.

first one: something + something ---> HSO3
second one: HSO3 + H <---> something

from the first equation when it makes HSO3 it shows that HSO3 will increase. As a result of Le Chatliers principle, it will shift the equilibrum to the right. As a result of the shift, the H ions will decrease thus the pH will go up

 

[Huy]

K2SO3 + H2O -> HSO3
HSO3 + H3O <--> ??

I think it was something like that.
I know water was in the 1st equation.
and the hydronium ion was in the second, with the product from the 1st.

 

[underthesun]

http://eat.epicurious.com/dictionary/wine/index.ssf?DEF_ID=2362&ISWINE=T

potassium metabisulfite
[puh-TAS-ee-uhm meht-uh-bi-SUHL-fite]
A white powder or salt containing approximately 57 percent sulfur dioxide. Potassium metabisulfite also comes in tablet form, known as Campden tablets. Meta, as it's also called, is dissolved in warm water before being used. When stirred into wine or must, it reacts with natural acids to release sulfur dioxide, which protects wines from unwanted bacteria and oxidation.

http://www.grapestompers.com/description_chem.htm
Potassium Metabisulfite
Potassium metabisulfite is added to wine to inhibit bacteria and yeast growth, as well as slow down oxidation. It may leave an unpleasant aftertaste in wine if the dose is too high. This chemical is also used in a water solution as an antiseptic rinse to sanitize equipment. It is identical to, but better than, Sodium Metabisulfite, because it does not add sodium to one's diet. CAUTION: Some people, particularly asthmatics, can have a severe allergic reaction to this substance.

I don't seem to be able to find any information that is relevant to it's effect with pH.. so I don't know. It'd suck so much, if the real full mark answer needs you to write something about oxidation / reduction etc..

 

[Ragerunner]

no. the question asks how it affects the pH only

 

[iambored]

hmm... yeah well i think i got it wrong coz i didnt even use the 1st equation

 

[howareya]

Originally posted by Ragerunner
I'm pretty sure im right. you have to look at both equations.

first one: something + something ---> HSO3
second one: HSO3 + H <---> something

from the first equation when it makes HSO3 it shows that HSO3 will increase. As a result of Le Chatliers principle, it will shift the equilibrum to the right. As a result of the shift, the H ions will decrease thus the pH will go up

yeah i agree....this is what i put down

 

[Ragerunner]

How about the fruit cannery question about 2 methods of monitoring waste water.

I put BOD and DO. not sure if im right. what u guys put ?

 

[Huy]

TDS and turbidity.

 

[littlemic21]

omg omg nooooooooooooooooo...
im soooooooo shtupid!
when it said name two INDICATORS i actually listed two pH indicators...
damn damn damn damn

 

[Ragerunner]

Originally posted by littlemic21
omg omg nooooooooooooooooo...
im soooooooo shtupid!
when it said name two INDICATORS i actually listed two pH indicators...
damn damn damn damn

hahahha. thats bad. at least you will give the teacher a good laugh i think that question was worth 4 marks though

 

[Chand]

lil mic..just think of this as a lesson...and in the hsc read the question properly first

 

[Ragerunner]

he did. just mis understood it

 

[Chand]

but then he didnt read it properly if he misunderstood

 

[Ragerunner]

true

what u guys get for the barium sulfate question ? what precautions to minimize accuracy ?

i said

heat it up and use multiple layers of filter paper or a scienterfilter

 

[Chand]

i made up crap..one was definitely to repeat the experiment and get average...another was to ensure that all equipment is clean so u dun get any foreign particles that can affect the weight...

 

[ded]

the test was pretty easy , all questions answered fully, no problems, i was expecting a harder cssa trials
or maybe im just too smart? Lol jkz hehehe good luck for the rest of ur trials guys

 

[howareya]

Originally posted by Ragerunner
true

what u guys get for the barium sulfate question ? what precautions to minimize accuracy ?

i said

heat it up and use multiple layers of filter paper or a scienterfilter

i said heat it to form max precipiate...ensure the vacuum was not to strong when attached to buchner funnel...ensure max precipites forms i.e. was heaps of Barium cholirde

 

[howareya]

i cant believe i stuffed up that ethanol qns!!!!!! in the multi choice

 

[Ragerunner]

relax its only 1 mark