chem-- paper 3--- w08

[AStarHunter]

guyz, how do you answer question 7(b)(iii) in this paper - variant 1-->http://www.xtremepapers.me/CIE/inde...CSE/0620 - Chemistry/&file=0620_w08_qp_03.pdf

Mark Scheme -->http://www.xtremepapers.me/CIE/inde...GCSE/0620 - Chemistry/&file=0620_w08_ms_3.pdf

Examiner`s Report --> http://www.xtremepapers.me/CIE/index.php?dir=Cambridge IGCSE/0620 - Chemistry/&file=0620_w08_er.pdf

Thnx !! :lol:

 

[xIshtar]

Butane is: C4H10, Chlorine is: CL2

So, C4H10 + Cl2 -> CH3-CH2-CH2-CHCL2 +H2.

 

[gary221]

guyz, how do you answer question 7(b)(iii) in this paper - variant 1-->http://www.xtremepapers.me/CIE/inde...CSE/0620 - Chemistry/&file=0620_w08_qp_03.pdf

Mark Scheme -->http://www.xtremepapers.me/CIE/inde...GCSE/0620 - Chemistry/&file=0620_w08_ms_3.pdf

Examiner`s Report --> http://www.xtremepapers.me/CIE/index.php?dir=Cambridge IGCSE/0620 - Chemistry/&file=0620_w08_er.pdf

Thnx !! :lol:

ok how about this

CH3-CH2-CH2-CH3 + Cl2 = CH3-CH2-CH2-CH-Cl2 + H2

thts wht i think it means by DIchloroethane!!!

 

[AStarHunter]

OH, and guyz, in the same paper as above in Q7(c)(iii) -is it alright if i drew it like this ? :

 

[AStarHunter]

Butane is: C4H10, Chlorine is: CL2

So, C4H10 + Cl2 -> CH3-CH2-CH2-CHCL2 +H2.

ok how about this

CH3-CH2-CH2-CH3 + Cl2 = CH3-CH2-CH2-CH-Cl2 + H2

thts wht i think it means by DIchloroethane!!!

I thought the same thing but this is what the examiner`s report said :

Most of those who attempted this question gave a
replacement reaction not substitution.
CH3–CH2–CH2–CH3 + Cl2 = CH3–CH2–CH2–CHCl2 + H2 :%) :crazy:

 

[gary221]

hey in this same ppr how do we calculate d amt of oxygen left (q 7 ai)

as 4 ur ques, i still feelthis is d correct ans.

 

[AStarHunter]

hey in this same ppr how do we calculate d amt of oxygen left (q 7 ai)

as 4 ur ques, i still feelthis is d correct ans.

I think i got the answer to my earlier question but I am not sure about the 2nd one ( the structure)

For your question (variant 1)
Basically, since we are dealing with gases, the mole ratio will be the same as the ratio in which the gases are produced. Since, oxygen is in excess and we want to find out the volume of oxygen left and the mole ratio is :

1 : 6.5 ---> 4 : 5
so, ratio of gases (using butane`s volume) is 10: 65 --> 40 : 50
and therefore, oxygen used is 65 cm^3 . to find oxygen left : 100 - 65 = 35 cm^3
Hope, this helped since it`s kind of hard for me to explain it ! :lol:

 

[xIshtar]

Butane is: C4H10, Chlorine is: CL2

So, C4H10 + Cl2 -> CH3-CH2-CH2-CHCL2 +H2.

ok how about this

CH3-CH2-CH2-CH3 + Cl2 = CH3-CH2-CH2-CH-Cl2 + H2

thts wht i think it means by DIchloroethane!!!

I thought the same thing but this is what the examiner`s report said :

Most of those who attempted this question gave a
replacement reaction not substitution.
CH3–CH2–CH2–CH3 + Cl2 = CH3–CH2–CH2–CHCl2 + H2 :%) :crazy:

So the report said what I said?


7(c)(iii) Is perfect, exactly what was needed to be drawn...

hey in this same ppr how do we calculate d amt of oxygen left (q 7 ai)

as 4 ur ques, i still feelthis is d correct ans.

Considering volume ratios..

1 : 6.5
10 cm^3 : 65cm^3..

100cm^3 - 65cm^3 = 35cm^3

For the volume of CO2.. The ratio of volumes is:

1 : 4.
10cm^3 : 40cm^3

=> 40cm^3 is formed..

Hope I helped guys, peace out

(Just saw that AStar posted an equally good explanation.

 

[gary221]

hey guys thnx 4 ur help...
i was always stumped by these ques!!! :wink: :wink: :wink:

 

[AStarHunter]

Butane is: C4H10, Chlorine is: CL2

So, C4H10 + Cl2 -> CH3-CH2-CH2-CHCL2 +H2.

ok how about this

CH3-CH2-CH2-CH3 + Cl2 = CH3-CH2-CH2-CH-Cl2 + H2

thts wht i think it means by DIchloroethane!!!

I thought the same thing but this is what the examiner`s report said :

Most of those who attempted this question gave a
replacement reaction not substitution.
CH3–CH2–CH2–CH3 + Cl2 = CH3–CH2–CH2–CHCl2 + H2 :%) :crazy:

So the report said what I said?


7(c)(iii) Is perfect, exactly what was needed to be drawn...

hey in this same ppr how do we calculate d amt of oxygen left (q 7 ai)

as 4 ur ques, i still feelthis is d correct ans.

Considering volume ratios..

1 : 6.5
10 cm^3 : 65cm^3..

100cm^3 - 65cm^3 = 35cm^3

For the volume of CO2.. The ratio of volumes is:

1 : 4.
10cm^3 : 40cm^3

=> 40cm^3 is formed..

Hope I helped guys, peace out

(Just saw that AStar posted an equally good explanation.

No, the report stated that it was wrong but i think finally got what they mean and that it is supposed to be a different structure. So instead of 1-chlorobutane, it is supposed to be 2-chlorobutane !
OMG! I asked the qs and answered it :Yahoo!:
Oh, and thnx for answering my structure qs

 

[sweetiepie]

check dix out it may help u do letme know....


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