# multipule choice answers (1 Viewer)

#### sneaky pete

##### Member
Originally posted by pdarkness
12.(D) it seems its right, but can someone tell me how you actually do it!?
for flourine its about 75, and the chlorine is about 70 (rough guesses), divide each of them by their atomic mass

carbon 25/12 = 2.08
flourine 75/19 = 3.94
chlorine 70/35.5 = 1.97

round them off..
carbon: 2
flourine: 4
chlorine: 2

What is the molecular formula for this compound?
• (a) CF2Cl
• (b) CF2Cl2
• (c) C2F3Cl3
• (d) C2F4Cl2

hope that formatting is ok
theres probably other ways of doing it but thats how i got D :|

#### mei_ling03

##### Ain't love grand.
lol you people are crazy.. either you have extraordinary memories or you guys are so pumped about the exams that you all brought the questions home to study again (i'm not making any ill judgements here... just think it's rather studious).
i can't take exams out of exam rooms only cos i know i'll be obessing over what i got until i get my marks back! oh well.. good luck with the results guys!

#### Ziff

##### Active Member
The multiple choice and the Option parts of the paper can be removed from the examination room...

#### mei_ling03

##### Ain't love grand.
yeah i know... the lady actually gave it to me so i threw it in the bin.. otherwise it will haunt me

#### lillaila

##### clear as ice
same answers 4 me here and there but i got these:
(the first page was all good)

6.c - i bloody guessed this after crossing out b
7.b - the U confused me in the last column
10.c or d - sooooooo stupid, i crossed out a!
11.b - a guess wow!
12.a - stupid meeeeee
15.c - dunno, guessed it

#### enemy

##### Member
I have no idea with answers are correct,iam lost now.but for 15 i did D.....

#### Shocker_85

##### Member
Originally posted by Hottieflossy
did anyone put D for question 13?
i did~

#### jm1234567890

15 is A

Originally posted by Frigid
i swear 5 could be A...
friggin wording is soooo fuckd! *protests*
....

hehe, i might beat you in chem now that you made that mistake

#### iambored

##### dum-di-dum
Originally posted by Hottieflossy
did anyone put D for question 13?
yeah
Originally posted by iambored
5. u sure? how do you use a filter funnel to find dissolved solids?
13.
z is more reactive than x
z is more reactive than y
x is more reactive than y
my reasoning is right, it is 13 d, look at the reasoning above, therefore z>x>y, if not tell me why

Originally posted by crazylilmonkee
i dont get why 15 is def D
i said A cos buffers dont change much when acids or bases are added but it doesnt mean it says completely constant, hence the slight curve..
Originally posted by ND
For 15 i put A, after the buffer has been 'overcome', it wouldn't decrease linearly (at least i don't think so), let's wait for phenol or mercury.
yeah I dont think so either, its a imo

Originally posted by SchizM
Hey iambored.....filtering will do something....its muddy river water bro and were determining dissolved solids
since when ok, the question was NOT ambiguous, I just didnt read it! Thanks
Originally posted by Frigid
Q5?
how the heck do you get option D (Q and S)?

S is filtration, if something is dissolved, it'll go straight thru your filter...
see above

#### iambored

##### dum-di-dum
1B
2D
3B
4B
5A damn the question
6C
7C
8B damn the diprotic
9C
10A
11B
12D
13D
14C
15A

can someone explain to me why 9 is a? is it alphabetical? i changed it at the last min..

N

#### ND

##### Guest
Yep they have to be in alphabetical order.

#### iambored

##### dum-di-dum
!!!! i am so mad. i knew i should have left it, i never change multiple choice questions

#### raj

##### New Member
the answer to 5 is 3 which is a ure teacher is a dik

#### woohoo

##### New Member
15 is A, no doubt. buffers stop pH change... in A, HCl is added and the buffer resists the change.. but it can only take so much & after 50mL of HCl the pH starts to decrease

it is definately not D because the buffer will not keep the exact pH & then all of a sudden once 50mL of HCl has been added go 'whoa! hang on, 50mL of acid is in me, time to drop pH at a constant rate'

#### william

##### Member
Originally posted by iambored
5. u sure? how do you use a filter funnel to find dissolved solids?
13.
z is more reactive than x
z is more reactive than y
x is more reactive than y
therefore... !! i put them the wrong way round, don't mind me, but u can use them to understand the question if you need to
that's right. the reason that ppl choose B is they think Y>X from the first one , Y>Z from the second one, then Z<X from the final one . however, is the metal that oxidized, so they are more reactive.

Last edited:

#### william

##### Member
Originally posted by sneaky pete
for flourine its about 75, and the chlorine is about 70 (rough guesses), divide each of them by their atomic mass

carbon 25/12 = 2.08
flourine 75/19 = 3.94
chlorine 70/35.5 = 1.97

round them off..
carbon: 2
flourine: 4
chlorine: 2

What is the molecular formula for this compound?
• (a) CF2Cl
• (b) CF2Cl2
• (c) C2F3Cl3
• (d) C2F4Cl2

hope that formatting is ok
theres probably other ways of doing it but thats how i got D :|
the easiest way is just look at the white column( amount mol), which is 2 , 4 and 2

#### lillaila

##### clear as ice
OMG ur right, geezez whats wrong wif me

#### mojako

##### Active Member
Originally posted by william
the easiest way is just look at the white column( amount mol), which is 2 , 4 and 2
That doesn't make the formula to be C2F4Cl2. It could also be CF2Cl (mass/mole-present comparison only gets you the ratio of the atoms thing... C, F and Cl).
However if you imagine/try to draw the structural formula for CF2Cl, you'll see that 1 bond would be unutilised (which can't be.. and it won't normally form double bond with that structure), so it's C2F4Cl2.