Radioactive material undergoes 1st order decay kinetics.
For 1st order decay, half life = 0.693/k
where k = rate constant
k = 0.693/half life = 0.693/8.02 = 0.0864 day-1
Now, for 1st order reaction,
k =
Given: t = 6.01d, initial conc. = 5mg
∴0.0864 =
∴ final conc. = 2.975 mg
Answer: C= 0.406 M
Explanation:
Solution.
ν
=
0.730
m
o
l
;
ν=0.730mol;
V
=
1.8
⋅
1
0
3
m
L
=
1.8
L
;
V=1.8⋅10
3 mL=1.8L;
C=0.730mol
1.8 L=0.406 M
C= 1.8L
0.730mol =0.406M
The student made a mistake because he did not convert a unit of volume from milliliters to liters. After all, molarity is defined as the number of moles of solute per liter of solution.