Chemistry: Post your doubts here!

[h4rriet]

thanx i love u but how did we get 0.1 i didnt get that thanx

The mole ratio of H2O:H2:O2 is 2:2:1. So if H2O loses 0.2 moles, H2 will gain 0.2 and O2 will gain 0.2/2=0.1 moles.

 

[kingos3111]

k wat abt may june 2006 q10

 

[radhika bhandari]

can anyone help with no.6 of M.J 2011 variant 1
also no.11,17,40 of M.J 2011 variant 2.I would be grateful with your help.

 

[Student12]

1. Construct balanced equations for the combustion of 1 mole (10 cm3) of methane and ethane. Take the moles to be the volume. CO2 will be a product; it'll react with KOH, so you can minus the moles of CO2 from the total volume of the products (i.e. volume of CO2 + H2O).
1. Construct a balanced equation.
1. Construct a balanced equation and use mole ratios.
2. Just take the moles to be the volume. SO2 and CO2 react with NaOH, so you'll minus their volumes from the total volume.
4. Count the electrons!
2. 1 C=C bond will take 1 mole of H2 when it becomes saturated. Count the number of C=C bonds initially, and the number of C=C bonds left after the reaction. Subtract the second from the first to get the number of moles of H2 used.
2. Because NaN3 decomposes to give Na also, which in turn reacts to give more N2. So technically this new N2 is actually coming because of the NaN3. You have to take it into consideration as well.
2. 100 grams of fertiliser contains 15 g of N2. So 14 grams will contain x moles. c=x/v.

Could you please show the working in detail i knw the methods..

 

[hope4thebest]

HERE YOU GO:

Tell me if you still don't understand; I'll try and make it more clear.

Question paper and question number?

 

[kingos3111]

k can u explaun now may june 2006 q10 also please

 

[A star]

can anyone help with no.6 of M.J 2011 variant 1
also no.11,17,40 of M.J 2011 variant 2.I would be grateful with your help.

link pls

 

[radhika bhandari]

link pls

 

[Alice123]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w08_qp_1.pdf
Q30
isnt it supposed to be 25 %??
n also Q39 h4rriet Jiyad Ahsan or anyone
thanks

 

[Jiyad Ahsan]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w08_qp_1.pdf
Q30
isnt it supposed to be 25 %??
n also Q39 h4rriet Jiyad Ahsan or anyone
thanks

Q 30!
okay here goes, so you know when we find the yield in an ester rxn we use the acid right?
so the mass of the ethanoic acid given is 30, which divided by the mr of the acid
30/60 = 0.5 moles
and in the end the ester formed has mass 22g while its mr is 88, moles of ester formed,
22/88 = 0.25 moles
so if 0.5 moles of acid produces o.25 moles of the ester, we have
(0.25/0.5) x 100 = 50%

hope you got it, dnt mind asking if u didnt.
i'll just do 39 and post it up in a bit

 

[h4rriet]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w08_qp_1.pdf
Q30
isnt it supposed to be 25 %??
n also Q39 h4rriet Jiyad Ahsan or anyone
thanks

30. (30+30)-18 (mass of water)=the mass of ester we're supposed to get.
39. The compounds in 1 and 2 are made from C3H7 free radicals. The compound in 3 is made from C2H5 and C4H9 free radicals.

 

[Alice123]

Q 30!
okay here goes, so you know when we find the yield in an ester rxn we use the acid right?
so the mass of the ethanoic acid given is 30, which divided by the mr of the acid
30/60 = 0.5 moles
and in the end the ester formed has mass 22g while its mr is 88, moles of ester formed,
22/88 = 0.25 moles
so if 0.5 moles of acid produces o.25 moles of the ester, we have
(0.25/0.5) x 100 = 50%

hope you got it, dnt mind asking if u didnt.
i'll just do 39 and post it up in a bit

Thankyou sooo much
i did understand
Best of luck fr yr exam

30. (30+30)-18 (mass of water)=the mass of ester we're supposed to get.
39. The compounds in 1 and 2 are made from C3H7 free radicals. The compound in 3 is made from C2H5 and C4H9 free radicals.

Thanks

 

[h4rriet]

Could you please show the working in detail i knw the methods..

If you know the method, then you should be able to do the working too.

 

[h4rriet]

Question paper and question number?

Oct/Nov 2004 paper 1.

 

[kkhizar1]

Can someone help me with j08 P1 Q2???

 

[A star]

http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_w12_qp_13.pdf Q26

 

[Jiyad Ahsan]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w08_qp_1.pdf
Q30
isnt it supposed to be 25 %??
n also Q39 h4rriet Jiyad Ahsan or anyone
thanks

Q39
ok here goes you see the 3 options given right? look closely at the 3rd option.. umm just open the file attached, it should make sense.. if it doesnt all you have to do is ask

 

[A star]

Q39
ok here goes you see the 3 options given right? look closely at the 3rd option.. umm just open the file attached, it should make sense.. if it doesnt all you have to do is ask

bro solve my query pls :/ cannot get it right :/

 

[h4rriet]

k wat abt may june 2006 q10

 

[Jiyad Ahsan]

bro solve my query pls :/ cannot get it right :/

im on it