Chemistry MCQ thread...

[Mobeen]

@hateexams , hope u get it .

 

[workinghard]

mobeen i did get da ans by it!!!
how did i?! *surprised*
doh urs is definitely rite 2!!!

 

[Hateexams93]

@hateexams ans is C i used da formula u mentioned n got it
try again or ll post it 2moro
i'm getting 2.72 and the answer is 2.67 ...it means there is something wrong with it

 

[kshumaila52]

SOME1 PLZZZZZZZZZZZZZZZZZZZZZZZZZZ HELP ME
The density of ice is 1.00 g cm–3.
What is the volume of steam produced when 1.00 cm3 of ice is heated to 323 °C (596 K) at a
pressure of one atmosphere (101 kPa)?
[1 mol of a gas occupies 24.0 dm3 at 25 °C (298 K) and one atmosphere.]
A 0.267 dm3 B 1.33 dm3 C 2.67 dm3 D 48.0 dm3
DO WE TO HAVE USE THIS FORMULA PV=nRT OR WHAT ????? I CAN'T GET THE ANSWER (((((((

by using density and vol of ice, find mass of ice, it ll be be ig(m=d x v), now find mole of ice 1/18(mass /Mr) now apply equation PV=nRT

 

[workinghard]

u go 4 mobeen's i ll post my method later
mobeens ll work fine !

 

[Mobeen]

mobeen i did get da ans by it!!!
how did i?! *surprised*
doh urs is definitely rite 2!!!

well i tried to do it by that formula ... but couldnt understand for a long time .. but my teacher explained it to me with this formula . and this formula makes it quite easier and less time consuming once u get it ..

 

[workinghard]

u r rite but i tried it da other way n yeah it wx time consumin
so thnx!!!!

 

[Mobeen]

@hateexams ans is C i used da formula u mentioned n got it
try again or ll post it 2moro
i'm getting 2.72 and the answer is 2.67 ...it means there is something wrong with it

yes i also got 2.67 with this formula .. but u check my working .. hope u understand that .

 

[Mobeen]

u r rite but i tried it da other way n yeah it wx time consumin
so thnx!!!!

welcome

 

[kshumaila52]

q.32 plz
http://www.xtremepapers.me/CIE/Internat ... _qp_11.pdf

its B
oxidation state (3) is wrong,

 

[workinghard]

@kshumaila52 sorry gal it is D u can chk markscheme 2!!!
dere's no change in oxidation in 2 either!

 

[kshumaila52]

SOME1 PLZZZZZZZZZZZZZZZZZZZZZZZZZZ HELP ME
The density of ice is 1.00 g cm–3.
What is the volume of steam produced when 1.00 cm3 of ice is heated to 323 °C (596 K) at a
pressure of one atmosphere (101 kPa)?
[1 mol of a gas occupies 24.0 dm3 at 25 °C (298 K) and one atmosphere.]
A 0.267 dm3 B 1.33 dm3 C 2.67 dm3 D 48.0 dm3
DO WE HAVE USE THIS FORMULA PV=nRT OR WHAT ????? I CAN'T GET THE ANSWER (((((((

we cant use pv=nrt in this .
we use v1/T1 = v2/T2
the initial vol =v1. the mass of ice cube is 1 (mass= density* vol) thus the moles of the water in ice cube would be 1/18.
the initial vol = moles * 24 = 1/18 *24 =1.333
the initial temp is rtp =298
the final temp is 596
so put in the formula
=> 1.333/298 = x/596 ( x = final vol of steam )

water is liquid, how vol of liquid become equal to mole * 24???
just find mole of ice and then at higher temperature (596K) it is in vapours form so apply pv=nrt.( red spot explanation is not satisfactory)
x 2.667 C

 

[kshumaila52]

@kshumaila52 sorry gal it is D u can chk markscheme 2!!!
dere's no change in oxidation in 2 either!

can you post question again??? year(paper) and question number??

 

[kshumaila52]

q.32 plz
http://www.xtremepapers.me/CIE/Internat ... _qp_11.pdf

its B
oxidation state (3) is wrong,

reallyyyyyyyyyyyyy soryyyyyyyy i checked 33

 

[Hateexams93]

WHY NOT A ?

 

[Mobeen]

@kshumaila52
the moles of water as a liquid and as a gas would be the same for that ice cube .. so thats why i multiplied it by 24 .. because in real i was multplying the moles of gas by 24 ..

 

[Mobeen]

WHY NOT A ?

P and v are inversely proportional to each other and it should decrease but with a curve . not a straight line .

 

[Hateexams93]

WHY NOT A ?

P and v are inversely proportional to each other and it should decrease but with a curve . not a straight line .

hmm.why it can't be a straight line ?

 

[kshumaila52]

WHY NOT A ?

ans is D
explanation: pv is constant so b and c are wrong, in case of A, graph is also direct relationship, with negative slope ( for inversely proportion check book)

 

[Mobeen]

the graph for inverse proportion is always a curve .. because i think there is a limit when the curve becomes horizontal .. but a straight line would cut the x-axis .. but the presure cant be zero right ? thats my logic for why it cant be a straight line .. but i do know that for every inverse graph it is a curve ..