Chemistry help

[bravegirl123]

Please explain how to solve MCQ# 16 in this paper: http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_s11_qp_11.pdf

 

[iKhaled]

Please explain how to solve MCQ# 16 in this paper: http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s11_qp_11.pdf

ok here concentrated sulfuric acid will not be able to oxidise NaCl or else we would have yellowish green gas formed so it is not stronger than chlorine but it will oxidize NaI because purple vapour is formed so conc H2SO4 is stronger than iodine so the answer is D and H2SO4 is stronger than H3PO4 because it can't even oxidize both of them

 

[bravegirl123]

Thanks i get it now

 

[bravegirl123]

I also need help in MCQ# 11 of this paper: http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_s11_qp_12.pdf

 

[autumnsakura]

I also need help in MCQ# 11 of this paper: http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s11_qp_12.pdf

no of mol of CO2 would be 72 /(1000 x 24) : 0.003 mol
Al compound + H20 = n CO2 + H20
We know that the only source of carbon is from the aluminium compound. This is actually a trial and error question.

If I try with solution A

Al2C3 + H20 = 3CO2 + H20 .... Ignore water because you only want to know the aluminium compound and CO2. Since there's 3 carbon in this compound of Al, there should be 3 in front of CO2 to balance the C's.

Mr of Al2C3: 90
no of mol of Al2C3: 0.144/90: 0.0016

1 mol of Al2C3 should give 3 moles of CO2
so 0.0016 x 3 should give 0.003. But it doesn't so this is not it.

If try with solution C

Mr of Al4C3: 144
no of mol : 0.001
When 0.001 x 3: 0.003mol
Thus C must be the answer.