Biology; Chemistry; Physics: Post your doubts here!

[Kamihus]

http://papers.xtremepapers.com/CIE/Cambridge International O Level/Chemistry (5070)/5070_s12_qp_42.pdf
Q4 plz help

Copper and zinc are the least reactive of the metals shown and will be displaced by any metal more reactive

 

[Saad Mughal]

http://papers.xtremepapers.com/CIE/Cambridge International O Level/Chemistry (5070)/5070_s12_qp_42.pdf
Q4 plz help

The reactivity series is:
Na .... Mg ..... Zn ..... Cu
The metal X displaces only 2 which means that it can only displace Zn and Cu.

 

[Suchal Riaz]

http://papers.xtremepapers.com/CIE/Cambridge International O Level/Chemistry (5070)/5070_s12_qp_42.pdf
Q4 plz help

only two. means least 2. if it reacts with another one that these two also. so there would have been reaction in three not 2.

 

[Saad Mughal]

man i have seen it in titration?

It is a neutral salt. It comes from Permaganese Acid HMnO4. It can be made alkaline/acidic by adding acid/alkali.

 

[Al-Anoud]

what r the type of biology ATP questions often asked ? and its answer. plzzzz help

drawing diagrams, food tests, and graphs. never saw a paper without them.

 

[Suchal Riaz]

http://papers.xtremepapers.com/CIE/Cambridge International O Level/Chemistry (5070)/5070_w12_qp_41.pdf
Q#9e

26.4 cm³ : 0.0025 mol
1000cm² : x
26.4 x=2.5
x=0.0947

 

[Suchal Riaz]

come on suchal and saad i have 2 sleep now plz tell me the method

there is reaction in 2 tubes only.
if it displaces Na that it is higher more reactive that Na means it is more reactive than all metals in tubes. so there will be reaction in 4 not 2 tubes.
it it displaces Mg that there will be reaction in three tubes
if it displaces Zn then it will also displace Cu as it is lower in reactivity seires. so only I and IV are tubes. if there was any other tube than the reaction would have been in more than 2 tubes. hope u understand.

 

[Suchal Riaz]

It is a neutral salt. It comes from Permaganese Acid HMnO4. It can be made alkaline/acidic by adding acid/alkali.

alright. here is an equation mustafa sent me: KMnO4 + KOH --> K2MnO4 + H2O
what do u say now. it looks correct.

 

[Khadija_1234]

AhsanAfzal Khadija_1234 please:
Potassium Manganate is a base? if yes what is it's formula and it's equation with reaction with an acid. and color change. everything we need to know about it.

It's also used to oxidize alcohols to produce Carboxylic acids

 

[AhsanAfzal]

http://papers.xtremepapers.com/CIE/...al O Level/Chemistry (5070)/5070_w08_qp_4.pdf
Q8 part (k) explain pls

 

[Suchal Riaz]

http://papers.xtremepapers.com/CIE/Cambridge International O Level/Chemistry (5070)/5070_w08_qp_4.pdf
Q8 part (k) explain pls

to keep the titration result constant moles must be same, as it is not made from 25 to 250, it's concentration must be increased by 10.

 

[AhsanAfzal]

can one drop of potassium magnate change colour of all the solution? Suchal Riaz

 

[TheStallion-Reborn]

can sum1 please help me with question 8d.. http://papers.xtremepapers.com/CIE/Cambridge International O Level/Chemistry (5070)/5070_s11_qp_42.pdf and for question 8(i) the marking scheme says 688/693 and my answer is 689.38. so will I get any marks?

 

[Khadija_1234]

can one drop of potassium magnate change colour of all the solution? Suchal Riaz

Yes

 

[TheStallion-Reborn]

can sum1 please help me with question 8d.. http://papers.xtremepapers.com/CIE/Cambridge International O Level/Chemistry (5070)/5070_s11_qp_42.pdf and for question 8(i) the marking scheme says 688/693 and my answer is 689.38. so will I get any marks?

Khadija_1234

 

[Khadija_1234]

http://papers.xtremepapers.com/CIE/...l O Level/Chemistry (5070)/5070_s12_qp_42.pdf
http://papers.xtremepapers.com/CIE/...al O Level/Chemistry (5070)/5070_w08_qp_4.pdf

Please help with Q4 of both papers

 

[TheStallion-Reborn]

http://papers.xtremepapers.com/CIE/Cambridge International O Level/Chemistry (5070)/5070_s12_qp_42.pdf
http://papers.xtremepapers.com/CIE/Cambridge International O Level/Chemistry (5070)/5070_w08_qp_4.pdf

Please help with Q4 of both papers

for the first one, the deposit will be formed when the strip will displace the ions present in the solution. this is done by a more reactive metal. so the least reactive metals (copper & zinc) will be deposited because they are most likely to be less reactive than metal x

 

[TheStallion-Reborn]

http://papers.xtremepapers.com/CIE/Cambridge International O Level/Chemistry (5070)/5070_s12_qp_42.pdf
http://papers.xtremepapers.com/CIE/Cambridge International O Level/Chemistry (5070)/5070_w08_qp_4.pdf

Please help with Q4 of both papers

for the next part it is zinc. its zinc because the last test tube contains cu ions so the metal has to be above copper in the reactivity series. so it's either aluminium zinc or calcium. but the second test tube contains N ions n the question says tht a deposit is formed on every piece of metal, so N has to be below magnesium in reactivity series, n that is zinc

 

[Khadija_1234]

Thanks a lot

 

[Khadija_1234]

for the next part it is zinc. its zinc because the last test tube contains cu ions so the metal has to be above copper in the reactivity series. so it's either aluminium zinc or calcium. but the second test tube contains N ions n the question says tht a deposit is formed on every piece of metal, so N has to be below magnesium in reactivity series, n that is zinc

But isnt aluminum also lower that Mg?