doubt in chemical kinetics.....

q.)
d activity of a radioactivity isotope falls to 12.5% in 90 days. find decay constant.

this ques. is solved in p bahadur....
it has used d eq. -

K= 2.30390log10012.5

but d eq. shud be

K= 2.30390log10087.5 na?
since [Nt] refers to d conc. left after time t...not at time t.....

1 Answers

logaa - x hai....and a - x is the amount left over. The question states that 12.5% is left over after 90 days. Hence a - x = 12.5%

√ √ || {} [] () → ~ ^ x x x → → ln log lg lim lim cos sin tan cot arcsin arccos arctan

∫ ∫ ∫ ∫ ∫ ∬ ∬ ∬ ∬ ∬ ∭ ∭ ∭ ∭ ∭ ⨌ ⨌ ⨌ ⨌ ⨌

∑ ∑ ∑ ∑ ∑ ∮ ∮ ∮ ∮ ∮ ∏ ∏ ∏ ∏ ∏ ∐ ∐ ∐ ∐ ∐

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° ∂ ∞ α β γ δ θ λ μ ν ξ π ρ σ φ ω ε ƒ κ τ υ Γ Δ Λ Σ Π Ω