40, To studythe kineticsof No, decomposition, a student measires the IN,ch! as a

Question

40, To studythe kineticsof No, decomposition, a student measires the IN,ch! as a ferwears of time The shadent then pkes the SINO! versus time aand I pyoJ versus lime and cloam nae plots The sadont correctly coachalesthe regard is order with a slope ayual to (A) find,-i first, (C) second,-t ED) second,t 70. A solution is preprod frorn 5.00 nLot2.00s I-M FelNOh and S rnL of 2.00-101 M KSCN whal are d" the intial concentrations of the Fe" and SCN" ions-paa mixing demo sohriins iscm 0K EA) 3.00-10-M B) 200x10'IM 2.00-10-a M (C) 19 10-t M 0.000 M 1.00x10 1 M [SoRNH [SofNM Pond it

Explanation / Answer

for 1st ordee reaction ,-d[A]/dt= K[A]

when integrated noting that [A]= [Ao] at t=0 and [A]= [A] at t=t gives

lnA= ln[Ao]- Kt, so a plot of lnA vs t if gives a straight line means the reaction is 1st order whose slope is -K

for second order, -d[A]/dt= K[A]2 , which when integrated, 1/[A]= 1/[A0]+Kt and hence 1/[A] vs t need to give strainght line.

since the plot of ln[A] vs t gave straight line, the order of the reaction is 1st with a slope of -K.( A is correct)

2.

Volume after mixing = 5+5= 10ml = 10/1000 L= 0.01M

Moles of Fe+3= 2*10-4*5/1000= 1*10-6, after mixing =1*10-6/0.01=100*10-6,

Similarly for SCN = 2*10-5*5/100/0.01= 100*10-6 , D is correct.

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