3A ---&gt; Practical exam HELP!

bump bump BUMP B U M P
Help someone please :frown:

Reply 2

icapturethecastle

je ne sais pas either

i'm worried...

Reply 3

Perhaps they want us to find the nolarity of the solution. I mean not neccessarily for an acid or base just any solution. Dunno just my 2 cents. I'm *******ing worried too!

Reply 4

Tell you what. Why dont we write down what we know on this thread and make this the standard thread for everyone to use? That way we dont have to start multiple threads for the same topic! Just write down the methods for the first three questions including precautions and perhaps together we can come up with the last question! Its worth a try!

Reply 5

Isnt there one of those model answers floating about? :biggrin:

LOL
Im VERY worried now.
Norality :s
Eeeek, thats a first :frown:

Reply 6

Sphixter meant molarity which is another way of expressing concentration. Unless you were joking and I made an idiot of myself. (Wouldn't be the first time either)
---
I think they might bring the use of a gas syringe where you plan to find the volume using the amount of gas that is evolved from the gas syringe (a reading), then calculate the moles of the gas using the equation moles = volume/ molar volume and then use ratios to travel across the equation and work out the concentration using moles which you calculated and the volume of the reactant (of which your supposed to work out the concentration for) you used in the reaction. There was a past paper question that made use of the gas syringe but it was "Planning an experiment to find the relative molecular mass of a Group 1 carbonate
M2CO3(s) + 2HCl(aq) → 2MCl(aq)+CO2(g)+H2O(l)"

Which uses some of the method of what I described. Maybe it's a similar reaction to this? But that's one method from what I remember.

Another method would be the titration method, but as you mentioned they are not likely to ask the same question twice as the method would be shown?

Reply 7

****
I feel hopeless.
I think its just a titration. LOL, im hoping it is!

Reply 8

Yeah, It would be much simpler if it was just a titration. I'm hoping it is too.

Reply 9

BTW, what are you feeling hopeless about maybe I can help? (sorry for double post)

Reply 10

Well, I havent touched unit 3 chemistry since, june 2007. You probably think Im joking, but im really not, Im just really caught up with my C2 and unit 3 bio retake which are both tomorrow. I plan to dedicate tomorrow night to unit 3 chem hopefully. But my problem is, that I dont even remember titration calculations, and the plan :| I havent got a CLUE. So, maybe I will just give up and wait for my rejections to come rolling in in August :frown:

Reply 11

Ah I feel for you. But don't give up just yet.
For one you need to stop worrying so much and focus on your exams for tomorrow. You shouldn't worry so much about the practical as I think you can take notes in with you. Even full blown textbooks in some colleges/schools :eek:

. But the 3B try revise more as no notes there :frown:

. As for the practical, my only advice is that if your good at cramming try and get some revision but don't stay up too late as you have your notes anyway AND you need your sleep. I read in a book that even people who are not so good in their theory can get top marks in practicals, as they are careful and carry out the experiments accurately.

As for the titration calculations I have a one or two documents that can search up for you and send to you.

Reply 12

I like you, youre nice :biggrin:

Made me feel better. Well its late now Im going to sleep but thankyou soooo much
:cool:

Reply 13

ayoushe

i havnt touched it yet either!! ugh i tht i was the only one!! its ok we can prepare in a night!! i have C2 today !! gd luck!

Reply 14

Someone-Else

Sphixter meant molarity

Thats right I did. Btw I think the reason why noone is replying to our desperate pleas for salvation is that not many people here do retakes and even then rarely in a practical. Those that generally know these things get it right the first time. So basically were *******ed

Reply 15

ayoushe

last time the questions were on here , and major hints were given out as some teachers leak them...lots of ppl got high A's cus of tht.

Reply 16

sphixter

Btw I think the reason why noone is replying to our desperate pleas for salvation is that not many people here do retakes and even then rarely in a practical. Those that generally know these things get it right the first time.

I agree, but we can still discuss what we think is going to come up.

In my opinion, Q1 will be relatively easier than the May paper last year. Will probably consist of a flame test, adding acid or base to the unknown and making observations and inferences. So all we need to do here is brush up on tests for anions, cations and gases.

Q2, will be a titration. My advice is take your time, do a dry run the first time to get a rough idea of where the equivalence point is. Then run it straight through to about 5cm3 before you get to the e.p. then carry on carefully. This way you can save a bit of time in the exam. Make sure that your pipette and burette are clean. Record burette readings to 2d.p. ending in 0 or 5. Phenolphthalein is the indicator we are using. Here is a site where it shows the titration before, at and after the endpoint. Click here
Here is a site going through titration calculations: Click Here

Q3,You will need to carry out a simple thermochemistry experiment.
I haven't got any ideas that I feel are going to come up. Maybe a enthalpy of neutralisation experiment, or maybe the enthalpy of reaction experiment will come up again. If someone else (not me :p:

) could bring up their thoughts it would be helpful.

Q4, I think this will be a titration but I think what we will have is a question where the compound which we have to find the concentration for is a solid. So we have to prepare a standard solution, and then carry out a titration. Or it could be the other possibility I explained about the gas syringe.

These are some of my thoughts, it's not that helpful but what can I do. :rolleyes:

Reply 17

Wait phenolphtalein indicator goes colourless to pale pink for acid to base right?
Also for question 1 you dont really need to know any tests. Its an open book test so you can see the tests there anyway. However it will be good for unit 3 b anyway so go ahead if your doing it. I hate the formula at the end part. Its really annoying because when carbonates, nitrates, etc are involved I keep forgetting their valencies and thus ******* up the formulae.
Anyway anyone here PM me your email addresses. That way we can find out how each of us had done before the timer on TSR gets over

Reply 18

ayoushe

is there a site where i can get 3A past papers and markschemes???!!!

Reply 19