Question

The half life period of decomposition of a compound is 50 minutes. If the initial concentration is halved, the half life period is reduced to 25 minutes. What is the order of reaction?

Answer 1

i think it is 1st

Answer 2

It's zeroth order. Look at the equation for a zeroth order half life:

\(t_{1/2}=\dfrac{[A_0]}{2k}\)

assume \([A_0]\)=1, and k=1, (I'm keeping values simple to make calculations easy)

then, \(t_{1/2}=\dfrac{[1]}{2(1)}=\dfrac{1}{2}\)

After the first half life the initial concentration decreased by half, \([A_0]=\dfrac{1}{2}\)
plugging it into the half life formula:

\(t_{1/2}=\dfrac{[\dfrac{1}{2}]}{2(1)}=\dfrac{1}{4}\)

The half life (\(t_{1/2}\)) was reduced by half after the first half-life period.