The compound Xe(CF3)2 decomposes in a first-order reaction to elemental Xe with a half-life of 30.0 min. If you place 4.5 mg of Xe(CF3)2 in a flask, calculate how long you must wait until only 0.25 mg of Xe(CF3)2 remains?

Answer : The time passed by the sample is,

Explanation :

Half-life = 30.0 min

First we have to calculate the rate constant, we use the formula :

Now we have to calculate the time passed.

Expression for rate law for first order kinetics is given by:

where,

k = rate constant  =

t = time passed by the sample  = ?

a = initial amount of the reactant  = 4.5 mg

a - x = amount left after decay process =0.25 mg

Now put all the given values in above equation, we get

Therefore, the time passed by the sample is,

- lead + phosphoric acid = hydrogen + lead(ii) phosphate

chemical digestion occurs in the stomach were hcl and pepsin forms chyme, the mouth in which salivary amylase breaks down starch to form bolus, and the small intestine specifically the duodenum.