PAPer 1 chemistry 2004

[1992]

Heelo. i need some help in M/J 2004: Q1, 3, 18, 23, 25, 30
and also O/N 2004: Q 3, 7,8,9,10 and 38. I know its a lot but chem for me is dificult especially mcq

 

[intel1993]

Mj 2004......
Q1)
find moles of the followings given and multiply it 6.02 * 10*23...........
mass of H = 1/1

so mass of neon 20/20
so it will gave the same ans as H wud give (ans = C)

 

[intel1993]

Q3) moles of sodium azide = 50/(23+ 14+14+14)

moles = 0.769

molar ratio of Na N3 : N2
2:3
so
2=3
0.769=x

x=1.15 mole

v = 24 into 1.15 = 27.7 dm3

 

[intel1993]

q18)
2 nacl + h20= 2 NaOh + cl2 + H2

58.5/(58.5)= 1 moles of Nacl

so now find out mass of h2 naoh n cl2... acc to molar ratio
u will get ur ans to be A

 

[intel1993]

Q23) cracking convert bigger hydrocarbon into smaller ones bt the ans given in D is even bigger than the substance which is cracked....

cont there r 10 carbon is the D option...........

so cannot be possible..

 

[intel1993]

Q25:

hey dude he ask which reaction cannot occur in catalytic converter.......................( or u cn say which dnot remove hazardous gases)

so we only read sum of these reaction occur in converter

co + no = co2 + N2

co + o2 = co2

option A contain the reaction wich is not possible and it aslo have carbon monooxide which is poisonous....

so Ans A

 

[intel1993]

Q 30:
2 mol of hcn will react with 2 mol of aldehyde that obvious ( nucleophillic addition)

so ans D

 

[intel1993]

hey dude in OCT nov 2004............... i also got 3 and 7 wrong so post u later after having discussion wid my frndz........

Q8)
pv =nrt
p= (1.6*10^3) ( 8.31) (273 + 273(k)) / ( 3*10^-3) as the volume is in dm^3 so divide it by 1000 to convert into m^3


so ans cum out to be D............

 

[intel1993]

q9)

listen always remember that always alkanes will release grater amount of enrgy of all.

then alkene n alkyne n so on....................so ans = B

all other were alcohol ketone n acid.....

 

[intel1993]

Q 10)

2 H20 = 2 h2 + o2
equlibrium 0.80(remains) 0.20 0.10 (distributed moles according to molar ratio)
0.20(REACTS)

so molar fraction moles/ total moles

now calculate it for every 1 n u will get the ans........

 

[intel1993]

Q 38)
in this question we will look to the bond energies....

if less bond energy than less time to break..

so c-br n c-I have less bond energy than c-cl as we know...

so option 2 n 3 r correct...........

bt if u see the difference between the orignal compund n option 1 u will notice that in option 1 C-h bonD(in orignal) is replaced by c-cl bond......

and aswe knoe that c-cl bond energy is less than c-h so it will also break faster just due to non presence C-h bond.............

so 1 also include in ans

so Ans = (1 2 3) A

 

[Amanina]

for Q3,

1mol of CH3SH react with 3 mol of O2,
so this means that 10cm3 of CH3SH react 30cm3 of O2.

since 60cm3 of O2 is used, there is 30cm3 of O2 left.

after reaction, produce gases (1 mol of CO2 and 1mol of SO2)
means 10cm3 of CO2 and 10cm3 of SO2

resultant mixture = 30cm3 of O2 + 10cm3 of CO2 + 10cm3 of SO2 = 50cm3.

 

[Amanina]

for Q7,

PH3 consists of 3bond pair and 1 pair of lone pair. so, it is trigonal pyramidal and the angle is about 107degree. answer B (104degree) is the nearest answer since C (109degree) is for tetrahedral (4bond pair)