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.
Helium - 4 isotope has 2 protons and 2 neutrons.
Its atomic number is 2 (the number of protons). Atomic number is the number of protons in the atom of an element and it identifies the element. All the isotopes of an element have the same atomic number (same number of protons). So, all the isotopes of hellium have 2 protons.
The number 4 that identifies the helium - 4 isotope is the mass number, i.e. the number of protons plus the number of neutron. So, helium-4 isotope has 2 protons and 2 neutrons. While, other isotopes of helium have 2 protons but different number of neutrons.
The atomic number enable us to deduce the number of electrons in an atom because the atoms are neutral, which implies that the positive and negative charge are equal. Given that the magnitude of the charge of electons and protons are equal but the sign is opposed (protons are positve and electrons are negative) the number of electrons in the atom equals the number of protonts. That is why the atomic number is also the number of electrons of the atom.
The answer is D. easier, higher
Not all units of measurement are equal, but the value of each unit is used for its intended purpose, so we have different units of measurement for each problem.
Answer: Yes, they do.
Explanation: Neutrons and protons are made up of smaller subatomic particles. When neutons and protons get get close to each other they convert particles and bond together. This occurance is called The Strong Force.
