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[Kamihus]

answer Q32, Q34

http://papers.xtremepapers.com/CIE/Cambridge International O Level/Chemistry (5070)/5070_s08_qp_1.pdf​

kamihus

32-P cant be copper as it doesnt react with HCl
Q is CuO as only it can be reduced with hydrogen as it is lower in the reactivity series
34-Carbon and Mg are the only solids
Carbon and CO burn to produce CO2 which is gaseous at r.t.p.
Thus only carbon satisfies both the requirements

 

[Kamihus]

38 A 10cm3 sample of a gaseous hydrocarbon is completely burnt in oxygen. The total volume of the products is 70cm3. All gas volumes are measured at room temperature and pressure.
Which equation represents the combustion of the hydrocarbon?
A CH4(g) + 2O2(g) → CO2(g) + 2H2O(g)
B C2H4(g) + 3O2(g) → 2CO2(g) + 2H2O(g)
C C3H8(g) + 5O2(g) → 3CO2(g) + 4H2O(g)
D 2C2H6(g) + 7O2(g) → 4CO2(g) + 6H2O(g)
answer is b
how??? explain me plz...

shouldnt it be C??

 

[ayesha121997]

shouldnt it be C??

sorry its c i mistakenly wrote wrong answer

 

[ayesha121997]

32-P cant be copper as it doesnt react with HCl
Q is CuO as only it can be reduced with hydrogen as it is lower in the reactivity series
34-Carbon and Mg are the only solids
Carbon and CO burn to produce CO2 which is gaseous at r.t.p.
Thus only carbon satisfies both the requirements

do copper react wid acid in compound form e.g copper oxide....??
when water is produced as product do that reaction is neutralisation????

 

[AhsanAfzal]

32-P cant be copper as it doesnt react with HCl
Q is CuO as only it can be reduced with hydrogen as it is lower in the reactivity series
34-Carbon and Mg are the only solids
Carbon and CO burn to produce CO2 which is gaseous at r.t.p.
Thus only carbon satisfies both the requirements

thnks

 

[Kamihus]

do copper react wid acid in compound form e.g copper oxide....??
when water is produced as product do that reaction is neutralisation????

copper oxide does react
it is neutralization as most metal oxides are bases, btw neutralization reactions are called so due to the salt as product, not water

 

[Kamihus]

sorry its c i mistakenly wrote wrong answer

as one mole of every gas occupies same volume at r.t.p (24 dm3)
take 10cm3 as 1 mole
70 cm3 would mean 7 times more moles
option C has a total of 7 moles in products so it is the answer

 

[ayesha121997]

as one mole of every gas occupies same volume at r.t.p (24 dm3)
take 10dm3 as 1 mole
70 dm3 would mean 7 times more moles
option C has a total of 7 moles in products so it is the answer

why to take 10 cm3???

 

[Kamihus]

why to take 10 cm3???

it is stated in the question

 

[ayesha121997]

it is stated in the question

thanks....u realy solved my big problem.....

 

[TheLeagueofShadows]

i guess B

Please explain why you chose B and not C or D.

 

[Kamihus]

Please explain why you chose B and not C or D.

C is sulphate ion
D is Sulfur trioxide
B is incorrect as sulfur can have valencies of 2,4 and 6 but never 3

 

[Kamihus]

aaaryt....thnku!

thnks

thanks....u realy solved my big problem.....

welcome please pray for me that i start studying and get A*s

 

[ayesha121997]

what is the state of gpI metals at rtp????

 

[ayesha121997]

welcome please pray for me that i start studying and get A*s

u dont need to study and widout it u will achieve A*....

 

[ayesha121997]

24 Alloys are usually harder than the metals from which they are made.
Which difference between the metals explains the greater hardness of alloys?
A atomic radii
B densities
C electrical conductivities
D relative atomic masses
a is answer how??????

 

[ayesha121997]

http://papers.xtremepapers.com/CIE/...al O Level/Chemistry (5070)/5070_s05_qp_1.pdf
question no 39 can any1 explain me....

 

[Kamihus]

what is the state of gpI metals at rtp????

they are solids and have a low melting point

 

[Saad Mughal]

welcome please pray for me that i start studying and get A*s

Yeah, start studying. The main problem.

 

[Kamihus]

http://papers.xtremepapers.com/CIE/Cambridge International O Level/Chemistry (5070)/5070_s05_qp_1.pdf
question no 39 can any1 explain me....

lets consider all the options (M.F.=molecular formula) (E.F.=empirical formula)
A-M.F. C2H4 E.F. CH2
B-M.F. C3H6 E.F. CH2
C-M.F. C4H8 E.F. CH2
D-M.F. C8H8 E.F. CH