Otago HSFY chat - archive

[greenglacier]

Hey [MENTION=13527]Kentception[/MENTION], welcome to MSO!

Hope to see you stick around and continue to post helpful stuff!

 

[Kception]

Hey would you be able to put the maths to it - this question also tripped me up. XD

 

[Profiterole]

Hey would you be able to put the maths to it - this question also tripped me up. XD

I don't see why not, since physics is multi-choice, I would presume (for this question) that any method, providing it gets the right answer would be fine?

Oh, and Welcome to MSO!

 

[Kception]

Cheers XD

 

[Kception]

Sorry my mistake - that was in response to the previous chemistry question on page 136....

 

[miss_universe]

Welocome

 

[Kception]

[TABLE="width: 100%"]
[TR]
[TD="align: left"]because the pHka, then the concentration and therefore the moles of CH3COOH and CH3COO- would have to be equal

[/TD]
[/TR]
[/TABLE]
so half of the CH3COOH would react with the NaOH to make CH3COO-


[TABLE="width: 100%"]
[TR]
[TD="align: left"]You would have half the CH3COOH left while the other half reacting to form CH3COO-

[TABLE="width: 100%"]
[TR]
[TD="align: left"]CH3COOH= CH3COO-

Answer is 0.4g.

because if it was 0.8g of NaOH, then it would react in a 1:1 mole ratio with CH3COOH. You wouldn't get any CH3COO- then. [/TD]
[/TR]
[/TABLE]
[/TD]
[/TR]
[/TABLE]

Could you please post the maths for this question please XD

 

[Sam]

Could you please post the maths for this question please XD

Ok so, pH has to = pka (4.76) so you just have to rearrange +log(Base/acid) so that it equals log(1) which = 0.

We know there is (I don't have the question in front of me) 0.02 mol/L of CH3COOH so we need to get 0.02 mol/L of NaOH so that log(0.02/0.02) = 0.
So just use basic stoichiometry stuff to work out which gives 0.02 mol/L and the answer comes out as 0.80g.

I think this is all correct, I haven't done the problem for a while now.

 

[noblelady777]

Thanks Jonathan810 and Kentception! You guys are awesome

 

[Ruth]

Does anyone know the dates for the rescheduled Anzac day cels labs? I was clever and didn't write them down

 

[Profiterole]

Does anyone know the dates for the rescheduled Anzac day cels labs? I was clever and didn't write them down

You go to the cells department and they give you a choice to restream i think

 

[Ruth]

You go to the cells department and they give you a choice to restream i think

Oh yeah I already have, we did it during the lab, it's just that I can only remember my restreamed lab is Tuesday and not what week it is haha

 

[Proshot]

Hey guys, with the last question from the 2010 chem practise terms test, were we meant to know it?

 

[Profiterole]

Hey guys, with the last question from the 2010 chem practise terms test, were we meant to know it?

No, it was suppose to be in the ATP/energy lecture (the lecture where the lecturer did a no-show) so its not examinable.

 

[keypadlocked]

Oh yeah I already have, we did it during the lab, it's just that I can only remember my restreamed lab is Tuesday and not what week it is haha

hey rurururuth, did you manage to find out which week your lab has been rescheduled to because I'm having the same problem haha.

 

[hermafish]

Hi guys, am I right in thinking that the PCC lecture is examinable in the mid-semester test?

 

[Sam]

Hi guys, am I right in thinking that the PCC lecture is examinable in the mid-semester test?

Yes.

 

[Ruth]

hey rurururuth, did you manage to find out which week your lab has been rescheduled to because I'm having the same problem haha.

My friend tells me that they're next week which makes sense. I'm going to the cels office today though bc she needs to restream as well, so I'll double-check then and let you know fo sho

 

[Proshot]

Hey guys, Is the striped slides on the PCC stuff we don't need to know, like in thermo?

 

[Sam]

Hey guys, Is the striped slides on the PCC stuff we don't need to know, like in thermo?

He said that the slide with "Thermoregulation can be impaired in many ways. For example:" is the stuff he wanted us to know. I'm 99% sure that was a rather large hint as to what his question will be about this year.