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Answer:
a) calculating the concentration at which 50% of the test organisms of a particular species die
Explanation:
Bioassays -
<u>Bioassays is an analytical method to assess the effect of marine pollutant on the organism by estimating the concentration at which 50% of the test organisms die after exposing the test organisms for a specified time.</u>
It can be done by quantitative or by qualitative experiment , or direct or indirect .
It is used to detect the biological hazards or give the quality assessment of the mixture .
It is also used for the monitoring the quality of water .
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Answer:
The age of the rock = 2800.6 million years = 2.8 billion years.
A simple method of analysis similar to Carbon dating is used to obtain the required age of the rock. Radioactive substances decay according to first order reaction kinetics. So, plugging all the required parameters into the general equation for amount of substance left in a first order decay gives us the age of the rock.
Explanation:
Half life of Uranium-235 = 700 million years (from literature)
The decay of radioactive substances follow first order reaction kinetics.
The general equation is given as
A(t) = A₀ e⁻ᵏᵗ
A(t) = Amount of radioactive substance left after a particular time = 6.25%
A₀ = initial amount of radioactive substance = 100%
t = time that has passed since the beginning = age of the rock = ?
k = decay constant
The decay constant is related to the half life (T) through the relation,
k = (In 2)/T
k = (0.693/700) = 0.00099 /million years
A(t) = A₀ e⁻ᵏᵗ
6.25 = 100 e⁻ᵏᵗ
0.0625 = e⁻ᵏᵗ
In e⁻ᵏᵗ = In 0.0625 = -2.7726
-kt = - 2.7726
t = (2.7726/0.00099) = 2800.6 million years
t = 2.8 billion years.
Hope this Helps!!!
<span>it is the study of human activities on the surface of the globe
(regions inhabited <span>by men)</span></span>
