The bacterial growth follows the rate law, dN/dt = kN where k is a constant and 'N' is the number of bacteria cell at any time. If the population of bacteria (number of cell) is doubled in 5 min find the time in which the population will be eight times of the initial one?
As dN/dt = kN (It is a Ist order reaction)
Integrated rate equation for Ist order reaction
k = 2.303/t log N/No
when t = 5 min, N = 2No
k = 2.303/5 log 2No/No
or k = 2.303/5 log 2
for N = 8No , t = ?
t = 2.303/k log 8No/No
By putting the value of k
t = log 8No/N
or t = = 15 min
A piece of wood from an archaeological sample has 5.0 counts min-1 per gram of C-14, while a fresh sample of wood has a count of 15.0 min-1g-1. If half-life of C-14 is 5770 yr, the age of the archaeological sample is
8,500 yr
9,200 yr
10,000 yr
11,000 yr
Two gases X (molecular weight Mx) and Y (molecular weight My; MY > MX) are at the same temperature T in two different containers. Their root mean square velocities are CX and CY respectively. If the average kinetic energies per molecule of two gases X and Y are EX and EY respectively then which of the following realation(s) is (are) true?
EX > EY
CX > CY
EX = EY = (3/2) RT
EX = EY = (3/2) kBT
A plot of ln K against 1/T (abscissa) is expected to be a straight line with an intercept on ordinate axis equal to:
R xSo
The following graph shows how t1/2 (half-life) of a reactant, R changes with the initial reactant concentration a0. The order of the reaction will be
0
1
2
3
The time taken for 10% completion of a first order reaction is 20 min. Then, for 19% completion, the reaction will take
40 min
60 min
30 min
50 min
The half-life of a radioactive element is 10 h. How much will be left after 4 h in 1 g atom sample?
45.6 x 1023 atom
4.56 x 1023 atom
4.56 x 1021 atom
4.56 1020 atom
Radioactivity of a sample (Z = 22) decreases 90% after 10 yr. What will be the half-life of the sample?
5 yr
2 yr
3 yr
10 yr