If 1000 molecules enter the first-order reaction and 500 of them disintegrate in 1 s, then how many molecules disintegrate in 2 s?

250 molecules

Explanation:

The number of molecules at the end of 1s are half the initial number of molecules.So, we can see that 1s is basically the half live.

For first order reactions t1/2=(ln2)/k

k=(ln2)/t1/2

k =(ln2)/1s

k =ln 2 /s

Because we know k ,we can use the integrated rate laws.

For 1st order:

ln[A]=ln[A]initial -kt

[A]= ?

[A]initial=1000

k=ln2

t=2s

ln[A]=ln[1000]-[ln 2 x 2]

ln[A]~5.521

[A]=e^(5.521)

    =250 molecules

Hope it helps:)

answer: the value of enthalpy change will be -152.80 kj.

solution:

pressure = 1atm , temperature = = 298 k

given that pressure and temperature are same in both gases , the number of moles of both gases can be determined by the ideal gas equation.

according to reaction 3 moles no are reacting with 1 mol of ,then 0.49 mol of no will react with moles of ozone that is 0.16 moles of ozone. since, no is limiting reagent and is an excessive reagent.

enthalpy change for the reaction between the given volumes of the gases is :