2. Incoming wastewater, with BOD5 equal to 200 mg/L, is treated in a well-run secondary treatment plant that removes 90 percent
of the BOD. You are to run a five-day BOD test with a standard 300-mL bottle, using a mixture of treated sewage and dilution water (no seed). Assume the initial DO is 9.2 mg/L. a. Roughly what maximum volume of treated wastewater should you put in the bottle if you want to have at least 2.0 mg/L of DO at the end of the test (filling the rest of the bottle with water). (answer in mL)
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An isotope of ₂₀⁴⁰X ⇒₂₀⁴⁴X
<h3>Further explanation </h3>The elements in nature have several types of isotopes
Isotopes are atoms that have the same number of protons and a different number of neutrons.
So Isotopes are elements that have the same Atomic Number (Proton)
In the following element notation,
X = symbol of elemental atom
A = mass number
= number of protons + number of neutrons
Z = atomic number
= number of protons = number of electrons, on neutral elements
For symbol of isotope X :
₂₀X⁴⁰ : atomic number = 20, mass number = 40
A. ₄₀²⁰X : atomic number = 40, mass number = 20, neutrons=20
B. ₂₀⁴⁰X²⁺ : atomic number = 20, mass number = 40, neutrons=20
C. ₂₁⁴⁰X : atomic number = 21, mass number = 40, neutrons=19
D. ₂₀⁴⁴X : atomic number = 20, mass number = 44, neutrons=22