Question

For an experimental study of the kinetics of hydrogen peroxide decomposition in which the pressure of oxygen or volume of oxygen is monitored as a function of time, what should the volume of oxygen collected or the pressure of oxygen be at time zero? Do you expect your plot to pass through the origin? If so, why? If not, why not?

Answer 1

The decomposition of HYDROGEN PEROXIDE is a first order reaction.The reaction is as follows

H₂O₂------->H₂O +1/₂O₂

FROM IDEAL GAS EQUATION WE HAVE

PV=NRT

WHICH CAN BE WRITTEN AS P=NRT/_V

SINCE ,N/_V IS MOLES PER UNIT VOLUME THAT IS CONCENTRATION

SO WE CAN WRITE EQUATION AS P=CRT WHERE C IS CONCENTRATION

SINCE R AND T ARE CONSTANTS, SO P IS DIRECTLY PROPORTIONAL TO CONCENTRATION ,C.

FROM EQUATION OF KINETICS,WE HAVE K=2.303/_Tlog(c₀ /c_t), where c₀ is inital concentration and c_t is concentration after time t.

since P is proportional to C,we have

K=2.303/_tlog(p₀ /p_t) where p₀ is initial pressure and p_t is pressure after time t.

In terms of moles ideal gas equation can be writte as K=2.303/_Tlog(v₀/v_t).

from this we can find volume and pressure of hydrogen peroxide after time t.

for plot to pass through origin we have:

rate=k(A)ⁿ where k is rate constant and (A)=concentration

taking log on both sides we get

log(rate)=log(k(A)ⁿ)

log(rate)=log(k)+nlog(A)

on comparing this equation with equation of straight line, y=mx +c

we have,y=log(rate), log(k)= constant

and mx=nlog(A)

we know that a straight line passes through origin if c=0 or the constant term is zero.

thus we conclude that the plot passes through origin.