Solution :
According to Chick's law
where, t = contact time
c = concentration of disinfectant
k' = lethality coefficient = 4.71
n = dilution coefficient = 1
4 log removal = % removal = 99.99
= 1 - R
= 1 - 0.9999
Now for plug flow reactor contact time,
= 0.01875 days
= 27 minutes
For CSTR, 
days
= 5.4 minute
There are 3 reactors, hence total contact time = 3 x 5.4
= 16.2 minute
Or
or 
∴ C x t = 1.955
For PFR, 
min
∴ C 
= 0.072 mg/L
For CSIR, 
min
mg/L
∴ Chlorine required for PFR in kg/day
(1 gallon = 3.785 L)
= 18.25 kg/day
Therefore we should go for PFR system.
Answer: hey nice to see you again, the answer is B. Microscopes allowed scientists to see the cells.
Explanation:
Answer: Bubbles formed would be evidence that a chemical reaction took place when the solutions were combined.
Explanation:
As it is given that both 
and HCl chemically combine together leading to the formation of NaCl, water and carbon dioxide gas. As the gas is forming and its formation will also form bubbles into the solution.
This formation of bubbles actually indicate that a chemical reaction has taken place. As molecules of a gas are held by Vander waal forces so, this gas will readily escape into the atmosphere.
Thus, we can conclude that bubbles formed would be evidence that a chemical reaction took place when the solutions were combined.
