HSC 2012-2015 Chemistry Marathon (archive) (2 Viewers)

[Fiction]

re: HSC Chemistry Marathon Archive

Ethanol burns completely in oxygen producing carbon dioxide and water.

Calculate the volume of liquid water formed when the products are condensed at 25degC and 100kPa atmosphere if 91g of ethanol is used in the reaction

C2H50H (aq) + 302 (g) --> 2CO2 + 3H20

Moles of Ethanol = moles of H20 / 3

therefore 91/ Molar Mass of ethanol = 3*Volume H20 / 24.79
Volume = (91 * 3 * 24.79)/ 46.068
= 146.906........
= 150 (2 sig fig) L

I have a funny feeling I stuffed up somewhere because the units don't look right lewl

 

[Fiction]

re: HSC Chemistry Marathon Archive

I believe he is talking about Acetic Acid. The question was: "State the four chemicals in an acetic acid solution." After that it asked: "Sketch a curve based on temperature and concentration of the acetic acid solution". The question gave the pH of the acetic solution as temperature increased in a tabulated format.

The question about the ethanoic acid was based on the back-titration of CaCO3. The question said that instead of reacting CaCO3 with excess HCl then titrating the remaining moles using NaOH, in order to find the mass composition of CaCO3 in a substance, what are the effects or impacts when you replace the HCl with ethanoic acid and explain your reasoning.

What does happen when you place a strong acid with a weak acid?

 

[Ekman]

re: HSC Chemistry Marathon Archive

What does happen when you place a strong acid with a weak acid?

Well first of all, CaCO3 is a weak base, and when a weak base and a weak acid react, partial neutralization occurs and there is an equilibrium. The impacts it would have is that the back-titration would not work anymore as, the moment you remove the 'excess' (assumptions being made here as well) acid to titrate, the equilibrium would shift, thus more acid is produced according to LCP. Thus no matter how many times you want to titrate the excess acid, more would be produced... (This is what I said in the exam btw, so I need a third-party judgement on this)

 

[Drsoccerball]

re: HSC Chemistry Marathon Archive

Woah half yearlies already? It's only week 6 :O
Which school is this?

Our schools ahead in every subject
For english we just finished modulr C
For physics finished space and motors
For chemistry finished POM and acidic
For maths ex 1 we just have projectile motion left
For ex 2 weve done complex polynomials graphs conics not sure if were ahead..

 

[Drsoccerball]

re: HSC Chemistry Marathon Archive

What does happen when you place a strong acid with a weak acid?

You mean replace right?

 

[Kaido]

re: HSC Chemistry Marathon Archive

dayum, our school completely behind compared to your :O

 

[Drsoccerball]

re: HSC Chemistry Marathon Archive

dayum, our school completely behind compared to your :O

How about you guys where are you up to for everything? I got physics half yearly on friday D:

 

[Fiction]

re: HSC Chemistry Marathon Archive

Well first of all, CaCO3 is a weak base, and when a weak base and a weak acid react, partial neutralization occurs and there is an equilibrium. The impacts it would have is that the back-titration would not work anymore as, the moment you remove the 'excess' (assumptions being made here as well) acid to titrate, the equilibrium would shift, thus more acid is produced according to LCP. Thus no matter how many times you want to titrate the excess acid, more would be produced... (This is what I said in the exam btw, so I need a third-party judgement on this)

lol I thought your question was about what happens, if you attempted to titrate ethanoic/acetic acid with HCl.

You mean replace right?

What, no. I meant place as in what happens if you titrated a weak acid with a strong acid?

 

[Ekman]

re: HSC Chemistry Marathon Archive

lol I thought your question was about what happens, if you attempted to titrate ethanoic/acetic acid with HCl.


What, no. I meant place as in what happens if you titrated a weak acid with a strong acid?

Well hopefully my teacher doesn't see this and put a question that is somewhat similar and harder than what you are suggesting...

 

[turntaker]

re: HSC Chemistry Marathon Archive

That feel when I am only up to Lashitayloers principle

 

[Ekman]

re: HSC Chemistry Marathon Archive

That feel when I am only up to Lashitayloers principle

Le Chatlier's Principle*

 

[turntaker]

re: HSC Chemistry Marathon Archive

Le Chatlier's Principle*

Yes or that

 

[turntaker]

re: HSC Chemistry Marathon Archive

Le Chatlier's Principle*

Sorry Mr/Mrs grammar nazi

 

[turntaker]

re: HSC Chemistry Marathon Archive

Jeez,....

 

[Ekman]

re: HSC Chemistry Marathon Archive

We covered that in week 2 at my school.

 

[turntaker]

re: HSC Chemistry Marathon Archive

We covered that in week 2 at my school.

Good for you.

 

[Drsoccerball]

re: HSC Chemistry Marathon Archive

lol I thought your question was about what happens, if you attempted to titrate ethanoic/acetic acid with HCl.


What, no. I meant place as in what happens if you titrated a weak acid with a strong acid?

You just use methyl orange to find the equivalence point right..

 

[Ekman]

re: HSC Chemistry Marathon Archive

You just use methyl orange to find the equivalence point right..

First of all, you cant titrate a weak acid with a strong acid, because there is no neutralization....

 

[futurecompscistudent]

re: HSC Chemistry Marathon Archive

what is ethanol

 

[Drsoccerball]

re: HSC Chemistry Marathon Archive

what is ethanol

I might need to do a little research on this one