Sig Figs / States etc on this year's exam...

[luken93]

I remember last year there was some debate on here regarding doing states and sig figs on questions in the exam.

Can anyone please clarify for me (and the rest of the Chemistry kids on here):
Sig Figs
 - I assume we show them for all questions where we make calculations
 - No that one comes to mind, but what if we had to do both multiplication and addition in a question, then which rule would apply?

States
 - Do we show states for all reactions
 - When is it (l) and when is it (aq), I always did (l) for H2O only, but apparently that's not the case...
          - Are there any specifics we need to know about in terms of certain reactions/reactants/products etc?

Thanks in advance.

[cltf]

Sig figs - ALWAYS to the least number of sig figs in the question.
States - ALWAYS in the final equation/answer. Eg. REDOX half equations don't need states, but the overall reaction does. Unless they split it up into separate questions, then it might be a safe bet to put in the states as it is the final answer.

[Greatness]

States - ALWAYS in the final equation/answer. Eg. REDOX half equations don't need states, but the overall reaction does. Unless they split it up into separate questions, then it might be a safe bet to put in the states as it is the final answer.

I think it would be safer to include states all the time. You dont want an examiner who's in a shitty mood to take of a mark or whatever for not inlcuding states. It's not that difficult to just add them in, and most the time you can probably guess what state they're in.

[luken93]

Yeah, that's what I was thinking, however apparently all esters are meant to be (l). Also, some alkanols and carboxylic acids are (l)

[Aurelian]

Sig figs - ALWAYS to the least number of sig figs in the question.

That can sometimes be misleading. Occasionally a question will have a piece of irrelevant information as a red herring - thus, to clarify, it's better to think of it as the least number of sig figs *used in calculations*.

[nacho]

I remember last year there was some debate on here regarding doing states and sig figs on questions in the exam.

Can anyone please clarify for me (and the rest of the Chemistry kids on here):
Sig Figs
 - I assume we show them for all questions where we make calculations
 - No that one comes to mind, but what if we had to do both multiplication and addition in a question, then which rule would apply?

States
 - Do we show states for all reactions
 - When is it (l) and when is it (aq), I always did (l) for H2O only, but apparently that's not the case...
          - Are there any specifics we need to know about in terms of certain reactions/reactants/products etc?

Thanks in advance.

for water I guess if you show a bit of logic like if there are high temperatures involved in a reaction, you'd put (g) or low temps at (s)
For acids and bases in neutralisation reactions they are always (aq)? and you'd be able to pick up common salts too. I'd say not to worry about it, states are generally pretty obvious.

I'd also like to know, is our working out required to be in sig figs, or is it just the final answer?

[Greatness]

I'd also like to know, is our working out required to be in sig figs, or is it just the final answer?

I've asked both my chem teacher about that and he said, it doesnt really matter as long as you stick to whichever one you're comfortable with. I normally round of to the required sig figures for the final answer.

[david10d]

It's usually just the final answer afaik. If you do use sig figures in your working out then that'll give an incorrect final answer. To be safe, I'd just write out sig figs if it gets the figure gets ridiculously long.

[Aurelian]

It's usually just the final answer afaik. If you do use sig figures in your working out then that'll give an incorrect final answer.

But that final answer won't be marked incorrect if you sig fig in working, provided you are consistent.

[Dr.Lecter]

I think he means if one were to constantly round off after every final value.

EDIT: But Aurelian is right in using sig fig in the initial calculation of mol, M...etc and to keep that consistent throughout the end.

[burbs]

In combustion, do you write H20 as (l) or (g). I'd have thought the latter...

[luken93]

In combustion, do you write H20 as (l) or (g). I'd have thought the latter...

Yeah see that's one of the things I'm talking about. I always have done CO2 (g) and H2O (l), but we could be wrong.

[jasoN-]

H2O is produced as gas (g) then it condenses as it cools down to liquid (l)

I'd assume both would be correct

[luken93]

For the others tuning in, this is the specific discussion I was talking about:

http://vce.atarnotes.com/forum/index.php/topic,26134.msg265392.html#msg265392

[nacho]

For the others tuning in, this is the specific discussion I was talking about:

http://vce.atarnotes.com/forum/index.php/topic,26134.msg265392.html#msg265392

It depends
If the acid is acting as an acid, it can't be liquid.
if your talking about combustion it cant be aq