Chemistry Paper 1 Doubts!

[maybeitwasnoone]

November 2008,
Questions,
2, (with a working please)
7 (Isn't Hydrogen supposed to be lighter)
9 (When its the other way around, won't it be negative delta H?)
14
17
19
22(What is monochloro-substitution? Something like only one Cl getting substituted? Explain the whole thing please)
30(With the working)
33(Why is 2 wrong?! :/)
38 and
39(Why is 3 wrong)

Thank You very much

 

[sweetiepie]

30 with working
%yield = actual mass /calculate mass x 100
22/44x100 = 50%

i hope it is clear to u..

 

[maybeitwasnoone]

30 with working
%yield = actual mass /calculate mass x 100
22/44x100 = 50%

i hope it is clear to u..

OMG its that, easy, I was doing some other crappy stuff.
Thanks A lot.

 

[sweetiepie]

hmm welcum ....

 

[Mobeen]

Q.2
10 cm3 CS2 reacts with 30cm3 O2 .. producing 10cm3 CO2 and 20 cm3 of SO2 . . (from the vol-vol ratio)
so the total vol of gas after burning is 10cm3 CO2 + 20 cm3 SO2 + 30cm3 excess O2 = 50 cm3

when excess NaOH is reacted both CO2 and SO2 will react with it because they are acidic oxides and NaOH is a base .. and no gas will be left except the excess O2 ... so final vol is 20 cm3
the answer is C.

 

[Mobeen]

Q7.
helium is the answer because the noble gases tend to show the most ideal gas behaviour .

 

[Mobeen]

Q9.
when its the other way round the activation energy would be higher .. and the enthalpy change would be positive because :
enthalpy change = energy of products - energy of reactants and the products would hav more energy in the reverse reaction than the reactants . so the difference of their energies would be positive .

 

[maybeitwasnoone]

Q.2
10 cm3 CS2 reacts with 30cm3 O2 .. producing 10cm3 CO2 and 20 cm3 of SO2 . . (from the vol-vol ratio)
so the total vol of gas after burning is 10cm3 CO2 + 20 cm3 SO2 + 30cm3 excess O2 = 50 cm3

when excess NaOH is reacted both CO2 and SO2 will react with it because they are acidic oxides and NaOH is a base .. and no gas will be left except the excess O2 ... so final vol is 20 cm3
the answer is C.

You meant 20cm3 excess O2 there,

Got it. Thanks

 

[maybeitwasnoone]

Q9.
when its the other way round the activation energy would be higher .. and the enthalpy change would be positive because :
enthalpy change = energy of products - energy of reactants and the products would hav more energy in the reverse reaction than the reactants . so the difference of their energies would be positive .

Don't we draw the diagram too the other way around, as in an exothermic diagram :/

 

[maybeitwasnoone]

And the other Questions too somebody.

 

[hassam]

helium size is also smaller than that of DIATOMIC H2gas....may be u selected hydrogen for this reason

 

[hassam]

17...its D ..phosphoric acid never acts as OXIDISING AGENT....WHEN sulfuric acid only liberates HYDROGEN HALIDE FROM corresponding halide salts....it is acting as an acid..bt when...it liberates iodine or bromine it is acting as an oxidising agent...

 

[maybeitwasnoone]

helium size is also smaller than that of DIATOMIC H2gas....may be u selected hydrogen for this reason

Yup I did choose Hydrogen. Got it now.
Other Questions too, Please.

 

[maybeitwasnoone]

Ummm, anybody?

 

[sweetiepie]

which ones u want maybe i wud help u if i can....

 

[maybeitwasnoone]

The 2nd, 9th, 14th, 19th, 22nd, 33rd, 38th and 39th.
I know its a heck of a list. :S

 

[aliya_zad]

q22) For chirality to exist each c atom shud have two different atoms or groups of atoms attached to it. In A,B,and C the c atom is attached to the same group, ie.h2, and ch3. Therefore the option is D.

 

[workinghard]

39 its B
cux if u split da molecules apart ... dats da places where radicals would be generated u must hv 3C on each sides to form C6 compound whch is xpected 4m us here
it is seen in A n B where u can draw a line b4 da branched carbon
in 3 its not possible bcux if u split dem apart one side would hv 2 carbon atoms n other would hv 4 ... hope u get wat am tryin 2 sy..
38
33only activation energy determines da RATE of forward reaction cux its da energy barrier dat needs 2 b crossed
da Kc n enthalpy change are actually kind of result of the reaction ... no?!
i mean after da reaction hx completed v decide what its Kc is n what da enthalpy change is
dats how i solved it
if deres anyother logic correct me 2!
14. aqSO2 is H2SO3 n aq NH3 is NH4OH so its an acid base reaction dat resuls in formation of (NH4)2SO3...
19 is D NH4+ v hv studid dat NH4+ hx capability f donating a proton n hence is an acid
while Mg(OH)2 is a base... again neutralization reaction
NacL is neutral so dats wy it does nt dissolve in it
9. da forward reaction is exo da reverse ll b endo n its activation energy ll b higher bcux wait ill attach a drawing.. to xplan...

 

[workinghard]

the second profile is for da reverse reaction
red line indicates activation energy
hope u do get it
cux i really m not good at xplnin things

 

[maybeitwasnoone]

39 its B
cux if u split da molecules apart ... dats da places where radicals would be generated u must hv 3C on each sides to form C6 compound whch is xpected 4m us here
it is seen in A n B where u can draw a line b4 da branched carbon
in 3 its not possible bcux if u split dem apart one side would hv 2 carbon atoms n other would hv 4 ... hope u get wat am tryin 2 sy..
38
33only activation energy determines da RATE of forward reaction cux its da energy barrier dat needs 2 b crossed
da Kc n enthalpy change are actually kind of result of the reaction ... no?!
i mean after da reaction hx completed v decide what its Kc is n what da enthalpy change is
dats how i solved it
if deres anyother logic correct me 2!
14. aqSO2 is H2SO3 n aq NH3 is NH4OH so its an acid base reaction dat resuls in formation of (NH4)2SO3...
19 is D NH4+ v hv studid dat NH4+ hx capability f donating a proton n hence is an acid
while Mg(OH)2 is a base... again neutralization reaction
NacL is neutral so dats wy it does nt dissolve in it
9. da forward reaction is exo da reverse ll b endo n its activation energy ll b higher bcux wait ill attach a drawing.. to xplan...

OMG Thank you soo much. <3