Answer: It will take 6.93 sec for tracer concentration to drop by 50% and 13.9 sec for tracer concentration to drop by 75%
Explanation:
Expression for rate law for first order kinetics is given by:
where,
k = rate constant =
t = age of sample
a = let initial amount of the reactant = 100 g
a - x = amount left after decay process
a) for tracer concentration to drop by 50%
a - x = amount left after decay process
= 50

It will take 6.93 sec for tracer concentration to drop by 50%
b) for tracer concentration to drop by 75 %
a - x = amount left after decay process
= 25
It will take 13.9 sec for tracer concentration to drop by 75%.
Answer : The original concentration of copper (II) sulfate in the sample is, 
Explanation :
Molar mass of Cu = 63.5 g/mol
First we have to calculate the number of moles of Cu.
Number of moles of Cu = 
Now we have to calculate the number of moles of 
Number of moles of Cu = Number of moles of 
Number of moles of
= 
Now we have to calculate the molarity of 

Now put all the given values in this formula, we get:

To change mol/L into g/L, we need to multiply it with molar mass of 
Molar mass of
= 159.609 g/mL
Concentration in g/L = 
Thus, the original concentration of copper (II) sulfate in the sample is, 
a. The unit cell is the smallest group of atom which have overall symmetry of a crystal, and from which is the entire letters can be buled built up by repetition in 3 dimensions.
b. The volume(v) of the unit cell is equal to the cell edge length (a)cubed.
c. density of polonium is 9.32g/cm3.
do you mean polymers or organic compounds?
Nothing at all happens because pure water cannot conduct electricity