FAQ for the Chemistry exam

[Collin Li]

Significant figures and states
Every paper has 1 mark for significant figures, and 1 mark for states. This means you can only lose 1 mark maximum, due to incorrectly doing your significant figures or states, but for those seeking to obtain these marks - don't fret. They only check one question to decide whether you pick up the mark or not. It is usually indicated by the question that says "express your answer to the appropriate number of significant figures" or "show all states." That will be the question they check for states, and they won't care about anything else, unless you state absurd amounts of significant figures.

A common concern regarding significant figures:
You only use the lowest number of significant figures out of all the numbers used in the calculations. So if a question tells you there are 0.5 grams of flowers and the question is about something else, it has no bearing on your significant figures.

Rounding
Many people ask this: do I round at each step, or do I round at the very end? Round at the very end - despite what the solutions suggest. The solutions are lazy! Round at the very end, it is the correct thing to do. I know that there are examples of the VCAA examiner reports doing it the lazy way, but the truth is that the examiner reports come out much later, and the examiners are marking from a different source as their solutions. If you save all the digits in your calculator, you can't go wrong.

Feel free to ask questions or add more here.

[iamdan08]

Wow. Thats cool! Where did you get that info from?

[cootcoot]

during reading time can you use your calculator?

[Mao]

nope =\ otherwise we'ld all be doing the stoic questions and storing the values on our calculator

scientific calculators cant store I dont think?

but no, cannot pick up anything during reading time.

[polky]

Mao: scientific calculators can store! Lol.  I don't know how to though xD

[AppleXY]

scientific calculators can store. But storing in sci. calcs are pain due to their limitations lol.

[shinny]

well yeh ild advise all of u to learn how to store (if ur calc can do it) coz it comes in handy for keeping the exact values of numbers for each question as u should be. particularly comes in handy in those questions where u burn hydrocarbons and have to continuously restart ur calculations since u gotta find n(C), n(H), m(C) etc, then back to n(C); its not a linear calculation like the type u do in titrations at all, so yeh, storing does come quite useful

[cara.mel]

It comes in handy if you're like me and just can't be bothered with writing out 6.02E23 or other constants. =)

[tiancaiyimu]

for those who dont know how to store values on their sci calc (casio fx-82AU) , all you have to do is this:
1. type value in
2. press shift
3. then the RCL button
4. lastly press any button that has the red letters above (7 options avalible, cant store in e)

[Collin Li]

well yeh ild advise all of u to learn how to store (if ur calc can do it) coz it comes in handy for keeping the exact values of numbers for each question as u should be. particularly comes in handy in those questions where u burn hydrocarbons and have to continuously restart ur calculations since u gotta find n(C), n(H), m(C) etc, then back to n(C); its not a linear calculation like the type u do in titrations at all, so yeh, storing does come quite useful

Yeah, but use Ans whenever possible for speed. Usually if you're clever you can work Ans into your next line, rather than storing (which is a bit cumbersome, IMO)

It comes in handy if you're like me and just can't be bothered with writing out 6.02E23 or other constants. =)

Yep, I do this, especially for Physics. I also use this in combination with my cheatsheet which tells me which letters on my calculator correspond to which constant. It's much safer dividing by as "A" rather than the number, because you might forget to put in brackets (fucking up your division)

for those who dont know how to store values on their sci calc (casio fx-82AU) , all you have to do is this:
1. type value in
2. press shift
3. then the RCL button
4. lastly press any button that has the red letters above (7 options avalible, cant store in e)

"Type value in" will lose you one or two decimal places. I think calculators store an extra digit or two "behind the screen." What I do with this calculator is, once I have the answer I want, I press "Ans", then "=", then press SHIFT-RCL (STO) and finally picking one of the pink letters above.

[pg88]

Oh I've learnt the hard way about screwing up the brackets... but yeah, thanks for the sig figs stuff...

Question - If I use the periodic table and grab a value of that, I would have to round to that number of sig figs right (suppose that the figs there are the smallest) because my teacher was really unclear and inconsistent about that

[Mao]

the accuracy is limited by the least accurate measurement. if the relative atomic mass has the least number of significant figures, then your answer would be limited by that.

[merlin]

Do VCAA ever set exam questions that are not included in the study design?

[Mao]

NO

well, they are not suppose to

[cara.mel]

However previous units are assumed knowledge, I think it was my year actually that a unit 4 question wanted you to calculate the pH of something, which was only dealt with in unit 3 (at the time, I'm not overly familiar with the new study design ), and a lot of people had already forgotten it.