Radioactive decay follows first-order kinetics. If a sample of I-131 decays from 25.0 mg to 8.25 mg in 12.8 days, what is the rate constant, k?

k = 0.0866 days⁻¹

Explanation:

The isotope decay of the atom follows the equation:

ln [A] = -kt + Ln[A]₀

Where [A] is the amount of the isotope after time t = 8.25mg

Time = 12.8days

k is rate constant

[A]₀ is actual amount of the isotope = 25.0mg

Replacing:

ln 8.25mg = -k*12.8days + ln 25.0mg

2.11 - 3.22 = -k*12.8days

-1.11 = -k12.8days

k = 0.0866 days⁻¹

here is table 2-2:

country

percent of eligible voters that voted

rank

united states

44.9%

138

canada

60.1%

107

costa rica

84.6%

14

hungary

66.9%

82

japan

57.0%

118

egypt

27.7%

159

south africa

85.5%

10

ans is no, the data set cannot be plotted as a single circle graph

answer: semi-infinite solid initially at a uniform temperature of 400 ◦c is cooled at its surface by convection. the cooling fluid at a constant temperature of 200 ◦c has a convective coefficient (ha) of 250 w/m2.k. the physical properties of the solid: k = 20 w/m.k and α = 4 * 10-5  m2/s. using δx = 0.04 m and δt = 10 s. write the finite difference equations describing the transient heat transfer of the first five δx and the temperature profile after 30 s.