4. The rate of a first-order reaction is 0.04 molL s-1 at 10 sec and 0

1.	4. The rate of a first-order reaction is 0.04 molL s-1 at 10 sec and 0.03 molLs-1 at 20 secafter initiation of the reaction. The half-lifeperiod of the reaction is [NEET 2016, Phase I(a) 34.1 s(C) 54.1 s(b) 44.1 S(d) 24.1 s
Answer» Reaction type : 1st order reaction Formula used : k =( 2.303/t2-t1) log([R1]/[R2]) Given :T1= 10 min andT2= 20 min therefore T2-T1= 10 min [R1] = 0.04 mol/L and [R2] = 0.03 mol/L Substituting the values in the above equation k =( 2.303/10) log( 0.04/0.03) k = 0.2303 [log(0.04) - log (0.03)] k = 0.2303 [-1.3979 - (-1.5228)] k = 0.02876 /min For the first order reaction half life t1/2is given by t1/2= 0.693/k We know, k = 0.02876 we get t1/2= 0.693/0.02876 t1/2= 24.096 min

4. The rate of a first-order reaction is 0.04 molL s-1 at 10 sec and 0.03 molLs-1 at 20 secafter initiation of the reaction. The half-lifeperiod of the reaction is [NEET 2016, Phase I(a) 34.1 s(C) 54.1 s(b) 44.1 S(d) 24.1 s

Answer»

Reaction type : 1st order reaction

Formula used :

k =( 2.303/t2-t1) log([R1]/[R2])

Given :T1= 10 min andT2= 20 min therefore T2-T1= 10 min

[R1] = 0.04 mol/L and [R2] = 0.03 mol/L

Substituting the values in the above equation

k =( 2.303/10) log( 0.04/0.03)

k = 0.2303 [log(0.04) - log (0.03)]

k = 0.2303 [-1.3979 - (-1.5228)]

k = 0.02876 /min

For the first order reaction half life t1/2is given by

t1/2= 0.693/k

We know, k = 0.02876 we get

t1/2= 0.693/0.02876

t1/2= 24.096 min