chem ppr 1 HELP PLEASEE!!

[tweez11]

9701/1,YR OCT/NOV 2OO2!
Q11...PLEASE EXPLAIN HOW TO SOLVE THIS,ITS ABOUT EQUILLIBRIA..I DONT KNOW HOWCUM THE FINAL ANSWER IS D!!
plz plz plz helpp!!!!
would be really really thankful:')

 

[PlanetMaster]

I'm assuming you're getting A ignoring the fact that x mol of the hydrogen iodide had dissociated!

 

[soumayya]

________________________2 HI ----> H2 + I2
Initially (in moles)__________b_______0___0
Amt dissociated(in moles)____x___________
Amt produced(in moles)___________(x/2)_(x/2)
Amt at equi(in moles)______(b-x)___(x/2)_(x/2)
_____________________________________________________________
Kp= (H2)(I2)/(HI) 2
Kp= (x/2) 2 /(b-x)2

rearranging it, u get x 2/4(b-x) 2

Hope it helps...

 

[tweez11]

Yea thanks i got it,i realize my mistake was not dividing the x by 2!
so yea planetmaster i initially thought its guna be A!
but then why do u have to divide the amount of dissociation(xmoles)by 2???
lyk isn't this actually giving the amount of both H2 and I2???

 

[soumayya]

2 moles of HI produces 1 mole of I2 and 1 mole of H2
so, x moles of HI produces (x/2) mole of I2 and (x/2) mole of H2