Question

For a firstorder reaction the timw required for 99.9% of

Answer 1

Answer:

Chemical Kinetics. Show that in first order reaction time required for completion of 99.9% is 10 times of half-life (t1/2) of the reaction.

A first order reaction has a rate constant 1.15 x 10–3 s–1.

Answer 2

Answer:

Explanation:

According to Integrated rate law expression:

K=2.303log(Ao/A)/t  where,

K is rate constant,

Ao is Initial Concentration of the substrate,

A is the left over concentration,

t is the time of reaction.

Therefore when99.9% of reactants have been changed into products;left over concentration equals to 100%-99.9%=0.1%.

Substituing the values in above equation and rearranging it we get:

t=2.303log(100/0.1)/k - (1)

Also given is that this time equals to 10 times half life of the reaction, so

t=10∗t1/2 - (2)

We know that t1/2=0.693/k

Equating (1) and (2) we get:

2.303log(100/0.1)/k=10∗0.693/k

=>6.90=6.93 (approx. )

Hence proved!