Doubts for paper 1 CHEMISTRY (AS-level)

[mohhef3]

plz participate guys

 

[mohhef3]

The following half reactions occur when potassium iodate(V), KIO3, in hydrochloric acid solution oxidises iodine to ICl 2 – .
IO3 – + 2Cl – + 6H+ + 4e– → ICl 2 – + 3H2O I2 + 4Cl – → 2ICl 2 – + 2e– What is the ratio of IO3 – to I2 in the balanced chemical equation for the overall reaction? A 1: 1 B 1 : 2 C 1 : 4 D 2 : 1
plz help guys question 4 paper 12 nov 2013

 

[fmwaz5]

1:2 answer is b because these are half equations and in order to add them up you need to make the number of electrons on either side in each equation equal so that they will cancel out. So you must multiply the second eq with 2 so you have 4e there as well. Now when you look at the ratio. It will be 1:2

 

[mohhef3]

1:2 answer is b because these are half equations and in order to add them up you need to make the number of electrons on either side in each equation equal so that they will cancel out. So you must multiply the second eq with 2 so you have 4e there as well. Now when you look at the ratio. It will be 1:2

thx alot mate appretiated

 

[mohhef3]

The compound ‘leaf alcohol’ is partly responsible for the smell of new-mown grass. CH3CH2CH=CHCH2CH2OH leaf alcohol What will be formed when ‘leaf alcohol’ is oxidised using an excess of hot, acidified K2Cr2O7(aq)?
A CH3CH2CH(OH)CH(OH)CH2CO2H
B CH3CH2COCOCH2CO2H
C CH3CH2CH=CHCH2CO2H
D CH3CH2CO2H and HO2CCH2CO2H
the answer is c but why D isnt possible

 

[Youknowwhoo]

anybody got a list / methods to memorise molecule shapes ? You know planar pyramid etc ? And bond angles ..: thanks ؟
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[Aly Emran]

The compound ‘leaf alcohol’ is partly responsible for the smell of new-mown grass. CH3CH2CH=CHCH2CH2OH leaf alcohol What will be formed when ‘leaf alcohol’ is oxidised using an excess of hot, acidified K2Cr2O7(aq)?
A CH3CH2CH(OH)CH(OH)CH2CO2H
B CH3CH2COCOCH2CO2H
C CH3CH2CH=CHCH2CO2H
D CH3CH2CO2H and HO2CCH2CO2H
the answer is c but why D isnt possible

Dude potassium dicromate cannot oxidise alkene! Remember that KMnO4 can oxidise an alkene but NOT K2Cr2O7

 

[sweetiepie94]

Tips For 31-40 (Chemistry MCQ's Paper 1)

. If 1st choice is obviously incorrect, the answer is automatically C.
. If 2nd choice is obviously incorrect the answer is automatically D.
. If 3rd choice is incorrect and 2nd choice is correct the answer is B.
. If 1st choice and 3rd choice are right the answer is A.

hope this helps everyone