The contents of a rock have a 206Pb to 238U mass ratio of 0.135:1.00. Assuming that the rock did not contain any 206Pb at the time of its formation, determine the age of the rock. Uranium-238 decays to lead-206 with a half-life of 4.5 billion years. Express the time to two significant digits.

The age of the rock is

Explanation:

The equation used to calculate rate constant from given half life for first order kinetics:

where,

= half life of the reaction = 4.5 billion years =    

Putting values in above equation, we get:

We are given:

Mass ratio of 206-Pb to 238-U = 0.135 : 1.00

Rate law expression for first order kinetics is given by the equation:

where,

k = rate constant  =

t = time taken for decay process = ? yr

= initial amount of the sample = [1.00 + 0.135] = 1.135 g

[A] = amount left after decay process = 1.00 grams

Putting values in above equation, we get:

Hence, the age of the rock is

2) Chloroform & Caustic potash

Explanation:

The carbylamine reaction is a kind of chemical test which is done to detect primary amines in an unknown solution. It cannot detect secondary and tertiary amines.

The reaction involves the heating with up of the unknown solution with alcoholic potassium hydroxide or caustic potash and the chloroform.

In the presence of primary amine, the production of isocyanide results.