Predictions for Chemistry 2014 HSC? (5 Viewers)

[SuchSmallHands]

Faisal Abdul wanted to find out how much ammonia was in his pee, so he titrated 25ml aliquots of his pee with 0.020M HCl 4 times.
The volume of the titres was as follows:
1. 27.98ml
2. 28.78ml
3. 27.78ml
4. 27.65ml

What was the concentration of ammonia in his pee?

This calc raises a serious question for me. If we did get a titration question and all of the values were this far off what do we say is the average? There are no two or three values that are nearly identical (I can't remember what the margin for error or whatever is, they told us at the STANSW Chem study day if any of you went to that, but I didn't write it down and my teacher didn't know. I think it was like 0.05 mL or something for titration?). So which of these values would you guys take to calculate average? 1, 3 and 4 maybe? Or just 3 and 4 even? (yeah I know this question wasn't meant to be so seriously considered haha)

 

[QZP]

Just to clarify, how do we neutralise strong base spills? Is it just simply adding NaHCO3? But this doesnt make sense... neutralising a strong base with a weak base?
I've heard that you're meant to add a strong acid and then NaHCO3 after

 

[QZP]

This calc raises a serious question for me. If we did get a titration question and all of the values were this far off what do we say is the average? There are no two or three values that are nearly identical (I can't remember what the margin for error or whatever is, they told us at the STANSW Chem study day if any of you went to that, but I didn't write it down and my teacher didn't know. I think it was like 0.05 mL or something for titration?). So which of these values would you guys take to calculate average? 1, 3 and 4 maybe? Or just 3 and 4 even? (yeah I know this question wasn't meant to be so seriously considered haha)

Yes you would take 1,3,4. I went to the national titration competition and trust me that is about as accurate you can get (let +- 0.2 be a general rule)

 

[SuchSmallHands]

Just to clarify, how do we neutralise strong base spills? Is it just simply adding NaHCO3? But this doesnt make sense... neutralising a strong base with a weak base?
I've heard that you're meant to add a strong acid and then NaHCO3 after

The HCO3- ion is amphiprotic, that's why we use it

 

[Queenroot]

This calc raises a serious question for me. If we did get a titration question and all of the values were this far off what do we say is the average? There are no two or three values that are nearly identical (I can't remember what the margin for error or whatever is, they told us at the STANSW Chem study day if any of you went to that, but I didn't write it down and my teacher didn't know. I think it was like 0.05 mL or something for titration?). So which of these values would you guys take to calculate average? 1, 3 and 4 maybe? Or just 3 and 4 even? (yeah I know this question wasn't meant to be so seriously considered haha)

There is usually an error of +- 0.05 for a burette, +/- 0.03 for a pipette and several other inaccuracies with equipment.
But for HSC's sake I'd say anything beyond +/- 0.5 is an error/outlier and not to count it as part of the average titre.

 

[enigma_1]

Just to clarify, how do we neutralise strong base spills? Is it just simply adding NaHCO3? But this doesnt make sense... neutralising a strong base with a weak base?
I've heard that you're meant to add a strong acid and then NaHCO3 after

you always neutralise spills (Acid/base) with NaHCO3 because upon neutralisation reaction, the heat released is far less than if you were to use a strong acid because the reaction is exothermic. It is a safety precaution pretty much.

 

[faisalabdul16]

did anyone do adrita's calculation question? hahaha

 

[enigma_1]

did anyone do adrita's calculation question? hahaha

haahha I thought it was for you.

I'm assuming you omit the rough titre? lol

 

[GOsie]

haahha I thought it was for you.

I'm assuming you omit the rough titre? lol

How did he stop-start pee so accurately? Bladder of steel

 

[enigma_1]

How did he stop-start pee so accurately? Bladder of steel

hahahhahah


eww this is becoming gross lol

k enough about faisal's pee

let's do some more chem ))

 

[faisalabdul16]

hahahhahah


eww this is becoming gross lol

k enough about faisal's pee

let's do some more chem ))

hhahahahah

some legit calc questions anyone?

 

[enigma_1]

hhahahahah

some legit calc questions anyone?

It's hard to find them, lol k here's a random one I found and I don't even know if it's hard

A sample of sodium hydroxide, NaOH, is known to have become contaminated with sodium carbonate, Na2CO3, by reaction with CO2 in the air. A 1.00g sample of NaOH is titrated with 0.500M HCl and it is found that 48.6mL of HCl are required for neutralization. Calculate the percentage by mass of Na2CO3 in the sample.)

 

[faisalabdul16]

It's hard to find them, lol k here's a random one I found and I don't even know if it's hard

A sample of sodium hydroxide, NaOH, is known to have become contaminated with sodium carbonate, Na2CO3, by reaction with CO2 in the air. A 1.00g sample is titrated with 0.500M HCl and it is found that 48.6mL of HCl are required for neutralization. Calculate the percentage by mass of Na2CO3 in the sample.)

1g of NaOH or Na2CO3

 

[enigma_1]

1g of NaOH or Na2CO3

1q of NaOH

fixed above too

 

[faisalabdul16]

Reading ROT's belonging essay, made me realise how shit mine is. =(

 

[enigma_1]

Reading ROT's belonging essay, made me realise how shit mine is. =(

omg same!!

gg band 6 ((((

but you know what I don't get, the exemplar responses in the hsc exam booklets things that you can buy - the answers are so shitty but they get good comments...? Are those answers even band 6 btw?

Coz They gave me hope, and now after reading other people's.....these hopes died

 

[faisalabdul16]

omg same!!

gg band 6 ((((

but you know what I don't get, the exemplar responses in the hsc exam booklets things that you can buy - the answers are so shitty but they get good comments...? Are those answers even band 6 btw?

Coz They gave me hope, and now after reading other people's.....these hopes died

I'm not sure. ROT's essay was just filled with techniques.

My essays in total with one related text have about 9 techniques, but they're all explained...

But then again, markers only mark one particular text i.e I'm doing the crucible, so the marker will only be marking this text.

BUT STILL, ROT's essay was beast...

Idk how im going to go in paper 1 now..

 

[enigma_1]

I'm not sure. ROT's essay was just filled with techniques.

My essays in total with one related text have about 9 techniques, but they're all explained...

But then again, markers only mark one particular text i.e I'm doing the crucible, so the marker will only be marking this text.

BUT STILL, ROT's essay was beast...

Idk how im going to go in paper 1 now..

yeah haha I don't have that many techniques either :/

I know right, all these fancy words and techniques...but don't worry, i'm sure your essay is very good!

Did you have a go at the question?

 

[faisalabdul16]

yeah haha I don't have that many techniques either :/

I know right, all these fancy words and techniques...but don't worry, i'm sure your essay is very good!

Did you have a go at the question?

Im hoping i get 13+

But it will be hard... These people and their essays WTF =(

I'll have a go now

 

[faisalabdul16]

I got 92%...

I think i am completely wrong