Chemistry Paper 1 Doubts Here... !

[xIshtar]

i have a question how can we sperate sulfur from sand ?

Hmm, if sand is silicon(iv) oxide, is it not soluble in an organic solvent, as it is a covalent compound? If not, I have no clue, sorry.

hey is sulfur soluble in water??

Do not believe so.. It's a simple non-metal after all.

 

[AStarHunter]

guyz, another chemistry doubt in this paper ---> http://www.xtremepapers.me/CIE/inde...GCSE/0620 - Chemistry/&file=0620_s05_qp_1.pdf

The mark scheme says B. Can someone explain why it is D and not B ?

Thnx

What question dude?

ardon: Sorry mate ! I forgot to include the question Anyway, it`s question 30

 

[narutogirl]

guyz, another chemistry doubt in this paper ---> http://www.xtremepapers.me/CIE/inde...GCSE/0620 - Chemistry/&file=0620_s05_qp_1.pdf

The mark scheme says B. Can someone explain why it is D and not B ?

Thnx

well you have to know the steps for the production of iron
the main reducing agent for this process is the carbon monoxide..now how is it done? first we have the carbon and oxygen react to form carbon dioxide..then we have this carbon dioxide reacting with the carbon to form the carbon monoxide..this now will react with the carbon monoxide
iron(3)oxide + carbon monoxide---> iron + carbon dioxide...(this is how iron oxide was reduced)

then the oxygen and oxygen oxides (like the CaO) is added to remove the impurities (we oxidise the impurities that are sulfur, phosphors, silicon and carbon)

i have a question how can we sperate sulfur from sand ?

Hmm, if sand is silicon(iv) oxide, is it not soluble in an organic solvent, as it is a covalent compound? If not, I have no clue, sorry.

all i know that sulfur isn't soluble in water either because it is an insoluble yellow solid..and i was thinking maybe it is soluble in an organic solvent..:/
oh n btw isn't covalent compounds soluble in most organic solvents?

 

[MohammedNoor]

http://www.xtremepapers.me/CIE/Cambridg ... 7_qp_1.pdf


in q 3 answer is A but it should be B as i think can anyone help me out



plz

Noor

 

[gary221]

http://www.xtremepapers.me/CIE/Cambridge%20IGCSE/0620%20-%20Chemistry/0620_s07_qp_1.pdf


in q 3 answer is A but it should be B as i think can anyone help me out



plz

Noor

see, u hve to look at d scale
it crosses the 5 mrk
hence it shud be mre than _5 sth not less thn
hence
d ans is A

 

[gary221]

why do u feel its B, anyway??

 

[narutogirl]

i have a question..does water affect the alkilinty and acidity of something?
and does it affect its reactions with other reactants?

 

[AStarHunter]

i have a question..does water affect the alkilinty and acidity of something?
and does it affect its reactions with other reactants?

All i know is that water makes an acid or alkali more dilute.
umm... not sure about the 2nd qs though. well, if it is electrolysis then ya, it would affect the final products that u get. But adding water to acids and alkalis, i don`t think it affects the actual reaction just whether they are more concentrated or dilute.

Hope it helps

 

[AStarHunter]

ok, quick question, why is the barium chloride obtained by crystallisation and not filtration in Q19 ( Answer is B) in this paper --> http://www.xtremepapers.me/CIE/inde...GCSE/0620 - Chemistry/&file=0620_w06_qp_1.pdf

Shouldn`t it be obtained the same way that barium sulphate is obtained- by filtration since barium sulphate is a precipitate ?
I am soo bad at this salt stuff :/

 

[Kokeeto]

Hey please help me, O/N 08, number 23. I don't know why the answer is A!!

 

[AStarHunter]

ok, quick question, why is the barium chloride obtained by crystallisation and not filtration in Q19 ( Answer is B) in this paper --> http://www.xtremepapers.me/CIE/inde...GCSE/0620 - Chemistry/&file=0620_w06_qp_1.pdf

Shouldn`t it be obtained the same way that barium sulphate is obtained- by filtration since barium sulphate is a precipitate ?
I am soo bad at this salt stuff :/

Another qs in the same paper as in the link above. Q27, why is it B and not A. Even if carbon does not reduce the magnesium oxide, won`t the carbon react with the air in the tube to form CO2 ? :shock:

 

[Kokeeto]

ok, quick question, why is the barium chloride obtained by crystallisation and not filtration in Q19 ( Answer is B) in this paper --> http://www.xtremepapers.me/CIE/inde...GCSE/0620 - Chemistry/&file=0620_w06_qp_1.pdf

Shouldn`t it be obtained the same way that barium sulphate is obtained- by filtration since barium sulphate is a precipitate ?
I am soo bad at this salt stuff :/

Another qs in the same paper as in the link above. Q27, why is it B and not A. Even if carbon does not reduce the magnesium oxide, won`t the carbon react with the air in the tube to form CO2 ? :shock:

xD yes it's B but you are so smart, and you ink deeply, which shouldn't be the case.. Good luck

 

[narutogirl]

ok, quick question, why is the barium chloride obtained by crystallisation and not filtration in Q19 ( Answer is B) in this paper --> http://www.xtremepapers.me/CIE/inde...GCSE/0620 - Chemistry/&file=0620_w06_qp_1.pdf

Shouldn`t it be obtained the same way that barium sulphate is obtained- by filtration since barium sulphate is a precipitate ?
I am soo bad at this salt stuff :/

well because barium chloride is soluble..because all salt halides except with lead and silver are soluble so that's why we crystalize..while barium sulfate is insoluble so we filter

Hey please help me, O/N 08, number 23. I don't know why the answer is A!!

because an acid can react with all of them but can't react with a salt..:/


i have a question in may/june 2004 number 30 :/..explain please

 

[AStarHunter]

ok, quick question, why is the barium chloride obtained by crystallisation and not filtration in Q19 ( Answer is B) in this paper --> http://www.xtremepapers.me/CIE/inde...GCSE/0620 - Chemistry/&file=0620_w06_qp_1.pdf

Shouldn`t it be obtained the same way that barium sulphate is obtained- by filtration since barium sulphate is a precipitate ?
I am soo bad at this salt stuff :/

well because barium chloride is soluble..because all salt halides except with lead and silver are soluble so that's why we crystalize..while barium sulfate is insoluble so we filter

Hey please help me, O/N 08, number 23. I don't know why the answer is A!!

because an acid can react with all of them but can't react with a salt..:/


i have a question in may/june 2004 number 30 :/..explain please

Ok, so for qs 30, basically, when they heat the alkali, water evaporates and thus, it is the distillate. As the pH of sodium hydroxide is high (like 12 or something) and the pH of the water is around 7 then thus the pH of the distillate (i.e. water) is lower.
Now, that you have evaporated the water, the aqueous sodium hydroxide has become more concentrated and thus, its pH is higher.

Hope, u get it

 

[xIshtar]

ok, quick question, why is the barium chloride obtained by crystallisation and not filtration in Q19 ( Answer is B) in this paper --> http://www.xtremepapers.me/CIE/inde...GCSE/0620 - Chemistry/&file=0620_w06_qp_1.pdf

Shouldn`t it be obtained the same way that barium sulphate is obtained- by filtration since barium sulphate is a precipitate ?
I am soo bad at this salt stuff :/

Another qs in the same paper as in the link above. Q27, why is it B and not A. Even if carbon does not reduce the magnesium oxide, won`t the carbon react with the air in the tube to form CO2 ? :shock:

It is B. Simply because of what you said, the MgO is too reactive to be reduced.. The carbon will not react with the air no..

 

[AStarHunter]

ok, another qs --> http://www.xtremepapers.me/CIE/inde...CSE/0620 - Chemistry/&file=0620_s10_qp_11.pdf
Q22, the answer is D but why can`t it be A ? Why didn`t they heat the solution ?!

 

[xIshtar]

ok, another qs --> http://www.xtremepapers.me/CIE/inde...CSE/0620 - Chemistry/&file=0620_s10_qp_11.pdf
Q22, the answer is D but why can`t it be A ? Why didn`t they heat the solution ?!

If you heat the crystals, you will remove the water. You want the crystals to remain hydrated, so it is counter productive. Hope I helped..


Good luck today man

 

[AStarHunter]

ok, another qs --> http://www.xtremepapers.me/CIE/inde...CSE/0620 - Chemistry/&file=0620_s10_qp_11.pdf
Q22, the answer is D but why can`t it be A ? Why didn`t they heat the solution ?!

If you heat the crystals, you will remove the water. You want the crystals to remain hydrated, so it is counter productive. Hope I helped..


Good luck today man

thnx mate ! good luck to u too, hopefully we`ll nail it 8)

 

[shan5674]

http://www.xtremepapers.me/CIE/Cambridg ... 7_qp_1.pdf

Can some one please explain number 35

please and thank you

 

[SalmanPakRocks]

Never Discuss the paper before 24 hours again or you will be permenantly banned !!!!!!!!!
I know people are discussing past papers here but two other members were involved in paper discussion !! please make a sperate topic for PAST PAPER discussion