HSC 2012-2015 Chemistry Marathon (archive) (1 Viewer)

[Crisium]

re: HSC Chemistry Marathon Archive

Does a buffer necessarily have to be a weak acid and its conjugate base? Or can it be a weak base and its conjugate acid? Since that's what I learnt.

Yeah I've been told that it can be either

 

[Anousha]

re: HSC Chemistry Marathon Archive

Does a buffer necessarily have to be a weak acid and its conjugate base? Or can it be a weak base and its conjugate acid? Since that's what I learnt.

Yes a buffer solution is one that contains comparable amounts of acid(H2CO3) and and its conjugate base(HCO3-), vice versa base with its conjugate acid, doesn't matter if its either it both maintains a constant pH

 

[Mr_Kap]

re: HSC Chemistry Marathon Archive

So saponification is the reverse of an estrification ---> where triglycerides + NaOH become glycerol and a carboxilic acid.

yeh??

 

[Mr_Kap]

re: HSC Chemistry Marathon Archive

Explain whether KOH can be used to make a suitable standard solution. 3 MARKS.

 

[Ekman]

re: HSC Chemistry Marathon Archive

So saponification is the reverse of an estrification ---> where triglycerides + NaOH become glycerol and a carboxilic acid.

yeh??

No, carboxylic acid is not formed in saponification. Instead 'salts' or 'soap molecules' are formed.

 

[Khan.Paki]

re: HSC Chemistry Marathon Archive

Anyone here doing shipwrecks (or should I say shipwrecked)? Any predictions? I reckon something about great depths and how corrosion was thought to be eliminated and titanic was found blah..blah.

 

[Crisium]

re: HSC Chemistry Marathon Archive

Explain whether KOH can be used to make a suitable standard solution. 3 MARKS.

The criteria used to assess its suitability would be:

* It's solubility

* It's reactivity (It should not react violently with the water solvent)

* It should have a high molecular mass (This puts off small measurement errors)

* Whether it has a known formula (Without this you cannot carry out the molar calculations to find the concentration of the titrant)

* Whether it is hygroscopic or non-hygroscopic

* Whether it is efflorescent or non-efflorescent

This is the sort of stuff I'd base my answer on but ceebs going into detail + I haven't skimmed over acidic yet ...

 

[Mr_Kap]

re: HSC Chemistry Marathon Archive

The criteria used to assess its suitability would be:

* It's solubility

* It's reactivity (It should not react violently with the water solvent)

* It should have a high molecular mass (This puts off small measurement errors)

* Whether it has a known formula (Without this you cannot carry out the molar calculations to find the concentration of the titrant)

* Whether it is hygroscopic or non-hygroscopic

* Whether it is efflorescent or non-efflorescent

This is the sort of stuff I'd base my answer on but ceebs going into detail + I haven't skimmed over acidic yet ...

thats exactly what you would talk about. They would probably ask NaOH though...prbably not KOH.

 

[Mr_Kap]

re: HSC Chemistry Marathon Archive

No, carboxylic acid is not formed in saponification. Instead 'salts' or 'soap molecules' are formed.

so a carboxyllic acid "salt" is formed ---> which is a 'soap'

 

[Ekman]

re: HSC Chemistry Marathon Archive

The criteria used to assess its suitability would be:

* It's solubility

* It's reactivity (It should not react violently with the water solvent)

* It should have a high molecular mass (This puts off small measurement errors)

* Whether it has a known formula (Without this you cannot carry out the molar calculations to find the concentration of the titrant)

* Whether it is hygroscopic or non-hygroscopic

* Whether it is efflorescent or non-efflorescent

This is the sort of stuff I'd base my answer on but ceebs going into detail + I haven't skimmed over acidic yet ...

Also to add to the criteria:

-Must be a solid

-If it can be obtained in pure form.

 

[Ekman]

re: HSC Chemistry Marathon Archive

so a carboxyllic acid "salt" is formed ---> which is a 'soap'

There is no acid to it lol. It has a COO- functional group, not a COOH functional group

 

[Mr_Kap]

re: HSC Chemistry Marathon Archive

An environmental officer measured the pH of a lake near a zinc mine and smelter. The zinc sulfide mined was roasted in air to produce crude zinc. The pH of the lake was 5.5.

What volume of gas (at SLC) would be released per tonne (1000kg) of zinc sulfide
refined? 2 MARKS

 

[Mr_Kap]

re: HSC Chemistry Marathon Archive

is analytical chemistry different to environmental chmistry??

 

[leehuan]

re: HSC Chemistry Marathon Archive

is analytical chemistry different to environmental chmistry??

What is environmental chemistry.

 

[leehuan]

re: HSC Chemistry Marathon Archive

Good luck

 

[Crisium]

re: HSC Chemistry Marathon Archive

Good luck

Good luck to you as well

 

[Crisium]

re: HSC Chemistry Marathon Archive

is analytical chemistry different to environmental chmistry??

They're very different ...

 

[Crisium]

re: HSC Chemistry Marathon Archive

Also to add to the criteria:

-Must be a solid

-If it can be obtained in pure form.

I read over my acidic environment notes and yeah it doesn't have to be extremely pure, BUT it must be able to undergo processes and what not to reach analytical reagent (AR) purity which is like 99.9% (which is also going to be your ATAR )

 

[Kaido]

re: HSC Chemistry Marathon Archive

Time to get the bs skills on, prepping for that 5 page 7 marker
Luckily, the 7mrk Qs are fairly similar for Shipwrecks

 

[Mr_Kap]

re: HSC Chemistry Marathon Archive

what are the bloody ozone equations??

i've seen like a billion of them in like a billion different orders.

Like im so confused.

I want: Ozone protecting us from UV eequations

AND

Ozone bein destroyed equations .

IN THE CORRECT ORDER !!! please somone