Question

Bismuth-212 has a half-life of 1 hour. If 40g of radioactive Bismuth-212 is collected, how much will remain radioactive after 5 hour?

Answer 1

Given Bismuth-212 has a half - life of 1 hour. General Equation of Decay function . s N = N_oe^-lambda t Where N_o - Initial quantity lambda - Decay rate t - time in hour Given half life of Ratio active element is d hour. (i.e it take 1 hour for element to reduce half to its Quantity) Therefore No/2 = No e^lambda(d) 1/2 = e^-lambda Taking ln both sides ln (1/2) = ln (e)^-lambda ln (1/2) = -lambda ln (e) [ln e = d] ln (1/2) = -lambda \r\n so lambda = 0.693d Now, Given No = 40g Therefore N = No e^0.693d t N =4o e^-0.6931 t Radioactive remained after 5 hours. N = 40(e)^-0.693d (5) N = 1.25 g so, after 5 hour d.25 g of ratioactive will remain