Unit 3B Chemistry :) How was the exams? Comment here :P

[Mufaddal]

i used 55

i used 55 too...i hope its correct

 

[Missyyy]

its the correct one: 2 P + 3 I2 = 2 PI3
check here: http://www.webqc.org/balance.php?reaction=P%2BI2%3DPI3

But isnt it supposed to be P4 instead of just P?

 

[qwerty123123]

its not correct, its the mass of the solution.

 

[jtbteddy]

Can someone please reply?

One more thing, for the diagram of distillation, I don't know why, but I put the thermometer in a test tube. It was in the correct place, but I just put it in a test tube, I don't know why, how many marks do you reckon I'd get out of 3?

I checked mark schemes of previous years for that diagram, the marks are for:
"Round-bottomed/pear-shaped flask (and
contents) and heat/mantle/water bath (1)
Still-head with stoppered thermometer
opposite opening to condenser (1)
Condenser with water flowing up(1)
Collection of product from an unsealed
apparatus either as shown or from a delivery
tube into a flask/beaker or straight from the
condenser into flask/beaker. (1)"

I did all the above perfect, except I put the thermometer in a test tube How much would I get for it?

 

[qwerty123123]

But isnt it supposed to be P4 instead of just P?

your right. from wikipedia: P4 + 6 I2 → 4 PI3

 

[qstar.inc]

alex replied to that already,

no idea...... so, just dnt wanna know anything.......

 

[qstar.inc]

your right. from wikipedia: P4 + 6 I2 → 4 PI3

lets then wait for the mark scheme to be released

 

[anan123456789]

i made a mistake by writing check the purity instead of redistillation,,what a mistake????

 

[anan123456789]

i was hoping for an A so that if i get a low mark in unit 2 its still an average mark, but it seems a bit hard now.

 

[anan123456789]

i used 55 too...i hope its correct

i think its wrong cuz the 5 should be negligible compared to the 50

 

[anan123456789]

in question 1 the alcohol part, i wrote instead of 1 degree and 2 degree aldehyde and ketone, is that considered wrong????

 

[Missyyy]

your right. from wikipedia: P4 + 6 I2 → 4 PI3

yay!

also, what did you write for that question about why it was washed with sodium thiosulfate rather than water alone??

 

[alex]

yay!

also, what did you write for that question about why it was washed with sodium thiosulfate rather than water alone??

to remove any unreacted Iodine

 

[Missyyy]

to remove any unreacted Iodine

Daaaammmmmmmmnnnn -____-

 

[Missyyy]

to remove any unreacted Iodine

and, last one why was the calcium chloride supposed to be ANHYDROUS?

 

[alex]

and, last one why was the calcium chloride supposed to be ANHYDROUS?

it's the drying agent, it's supposed to remove water if i'm not mistaken

 

[Manasa]

umm just wondering.... will i be not given a mark if in the first question i just said primary alcohol instead of aldehyde?>
/

 

[jtbteddy]

and, last one why was the calcium chloride supposed to be ANHYDROUS?

to prevent any side reactions

 

[jtbteddy]

umm just wondering.... will i be not given a mark if in the first question i just said primary alcohol instead of aldehyde?>
/

the answer is primary and secondary alcohol .. it isn't an aldehyde bcoz aldehydes don't have OH group, and the sample clearly has an OH group sincce misty fumes were formed when tested with PCl5

 

[Missyyy]

to prevent any side reactions

oh well