`._(19)K^(40)` consists of 0.012% potassium in nature. The human body contains 0.35% potassium by weight. Calculate the total radioactivity resulting from `._(19)K^(40)` decay in a 75 Kg human body. Half life of `._(19)K^(40)` is `1.3 xx 10^(9)` years

Radioactive decay follows first-order kinetic. The mean life and half-life of nuclear decay process are tau = 1// lambda and t_(1//2) = 0.693//lambda . Therefore are a number of radioactive elements in nature, their abundance is directly proportional to half life. The amount remaining after n half lives of radioactive elements can be calculated using the relation: N = N_(0) ((1)/(2))^(n) Half life of .^(60)Co is 5.3 years, the time taken for 99.9% decay will be

In a radioactive sample. ._(19)^(40)K nuclei either decay into stable ._(20)^(40)Ca nuclei with decay constant 4.5 xx 10^(-10) per year or into stable ._(18)^(40)Ar nuclei with decay constant 0.5 xx 10^(-10) per year. Given that in this sample all the stable ._(20)^(40)Ca and ._(18)^(40)Ar nuclei are produced by the ._(19)^(40)K nuclei only. In time t xx 10^9 years. If the ratio of the sum of stable ._(20)^(40)Ca and ._(18)^(40)Ar nuclei to the radioactive ._(19)^(40)K nuclei is 99. The value of t will be. [Given : In 10 = 2.3]

What is the pH of a 0.20 M HA solution (K_a=1.0xx10^(-6)) that contains 0.40 M NaA ?

Calculate the pH at equivalence point when a solution of 0.10 M acetic acid is titrated with a solution of 0.10 M hydroxide (K_(a) " for acetic acid is " 1.9 xx10^(-5))

In a container containing 0.2 kg of water at 40^@C , 0.2 kg of ice at 0^@C is mixed. Calculate the heat of fusion of ice if the resulting temperature is 5.5^@C . Take, Specific heat of water = 4186 J kg^(-1)K^(-1)

In a Moon rock sample the ratio of number of (stable) ""^(40)Ar atoms present to the number of (radioactive) ""^(40)K atoms is 10.3. Assume that all the argon atoms were produced by the decay of potassium atoms, with a half life of 1.25xx10^(9)y . How old is the rock?

In moon rock sample the ratio of the number of stable argon- 40 atoms present to the number of radioactive potassium -40 atoms is 7:1 . Assume that all the argon atoms were produced by the decay of potassium atoms, with a half-life of 2.5xx10^(9)yr . The age of the rock is