Question

At 150°C the decomposition of acetaldehyde CH3CHO to methane is a first order reaction. If the

rate constant for the reaction at 150°C is 0.029 min, how long does it take a concentration of
0.050 mol L of acetaldehyde to reduce to a concentration of 0.040 mol L?

Answer 1

The decomposition time : 7.69 min ≈ 7.7 min

Further explanation

Given

rate constant : 0.029/min

a concentration of 0.050 mol L to a concentration of 0.040 mol L

Required

the decomposition time

Solution

The reaction rate (v) shows the change in the concentration of the substance (changes in addition to concentrations for reaction products or changes in concentration reduction for reactants) per unit time

For first-order reaction :

[A]=[Ao]e^(-kt)

or

ln[A]=-kt+ln(A0)

Input the value :

ln(0.040)=-(0.029)t+ln(0.050)

-3.219 = -0.029t -2.996

-0.223 =-0.029t

t=7.69 minutes