Answer:
There are required 70.1 years for the activity of a sample of cesium-137 to fall to 20.0 percent of its original value
Explanation:
The radioactive decay follows always first-order kinetics where its general law is:
Ln[A] = -Kt + ln[A]₀
<em>Where [A] is actual concentration of the atom, k is rate constant, t is time and [A]₀ is initial concentration.</em>
We can find rate constant from half-life as follows:
<em>Rate constant:</em>
t(1/2) = ln 2 / K
As half-life of Cesium-137 is 30.2 years:
30.2 years = ln 2 / K
<em>K = 0.02295 years⁻¹</em>
Replacing this result and with the given data of the problem:
Ln[A] = -Kt + ln[A]₀
Ln[A] = -0.02295 years⁻¹* t + ln[A]₀
Ln ([A] / [A₀]) = -0.02295 years⁻¹* t
<em>As you want time when [A] is 20% of [A]₀, [A] / [A]₀ = 0.2:</em>
Ln (0.2) = -0.02295 years⁻¹* t
70.1 years = t
<h3>There are required 70.1 years for the activity of a sample of cesium-137 to fall to 20.0 percent of its original value</h3>
Answer is: Keq = [CO₂].
Balanced chemical reaction: CaCO3(s) ⇄ CaO(s) + CO₂(g).
The equilibrium constant (Keq) is a ratio of the concentration of the products to the concentration of the reactants.
Pure liquids (shown in chemical reactions by appending (l) to the chemical formula) and solids (shown in chemical equations by appending (s) to the chemical formula) not go in to he equilibrium constant expression, only gas state (shown in chemical reactions by appending (g) to the chemical formula) reactants and products go in to the equilibrium constant expression.
<h2>Answer : Daniel was related to study of Earth and Space
</h2><h2>Whereas Sanya was closely related to chemistry</h2><h3>Explanation :</h3>
As in the given information, Daniel the scientist was studying the effect of tropical storms on coastal erosions. These studies comes under the field of Earth and Space. Earth because coastal erosions are involved in the study, and Space because storms are discussed which is something related to space.
In case of Sanya, it is clear that her study focuses on discharges from the industrial plant that has effect on freshwater swamps. Precisely, she is studying the pH concentration which comes in chemistry.
This prove that Daniel studies Earth and Space whereas Sanya studies Chemistry.
