A Geiger counter registers a count rate of 4,800 counts per minute from a sample of a radioisotope. Sixteen minutes later, the count rate is 1,200 counts per minute. What is the half-life of the radioisotope?

Answer : The half-life of the radioisotope is, 8.00 min

Explanation :

First we have to calculate the rate constant.

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

where,

k = rate constant = ?

t = time passed by the sample  = 16 min

a = initial amount of the reactant  = 4800

a - x = amount left after decay process = 1200

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

Now we have to calculate the half-life.

Therefore, the half-life of the radioisotope is, 8.00 min

d) physical means can be used to separate the components of air.

answer: 2×10^-2kg

explanation: density= mass per volume

vol=mass/density

converting to s.i units we have;

3÷1000kg = 0.003

1.5÷100m = 0.15

0.003/0.15 = 0.02kg