03-01-2017, 07:35 PM
(This post was last modified: 03-01-2017, 07:51 PM by SunilNagpal.)

It was a classical case of zero order kinetics:

Concentration left at any time, t = -kt + Initial concentration

So that, 0 = -kt + 0.1

ie t = 0.1/1000 = 100 mins

The problem with unitary method is very interesting though ( something that will fetch you all some marks on this question).

A zero order reaction can easily be approached using a unitary method (provided the question setter stays alert in keeping all the units in sync). This time they messed with the unit of k (by giving its unit as mol per min) whereas in a zero order reaction, k is supposed to be mol per litre per min or say concentration per minute).

So, it's a mistake at examiner's end in giving wrong units for the reaction constant. Those who used classical formulas got the right answer, but those who were more analytical in this question ended up on the wrong road.

In my view, both the 100 and 10,000 are are right answers in students' perspective, the mistake is at examiner's end.

Concentration left at any time, t = -kt + Initial concentration

So that, 0 = -kt + 0.1

ie t = 0.1/1000 = 100 mins

The problem with unitary method is very interesting though ( something that will fetch you all some marks on this question).

A zero order reaction can easily be approached using a unitary method (provided the question setter stays alert in keeping all the units in sync). This time they messed with the unit of k (by giving its unit as mol per min) whereas in a zero order reaction, k is supposed to be mol per litre per min or say concentration per minute).

So, it's a mistake at examiner's end in giving wrong units for the reaction constant. Those who used classical formulas got the right answer, but those who were more analytical in this question ended up on the wrong road.

In my view, both the 100 and 10,000 are are right answers in students' perspective, the mistake is at examiner's end.

(03-01-2017, 06:09 PM)sadaf188 Wrote:(03-01-2017, 06:01 PM)travellingsalesman Wrote: Nope. Its a different question. Same answer!Yes the question is....a zero order kinetics.......

If we follow even simple unitary method also then...

1min........10^-3 moles consumed

100min....0.1 moles consumed

Whereas conc of A is 0.1moles/liter....so for 100litre its is 0.1*100=10 moles.

So for 10 moles...10000 min are required