<u>Answer:</u> The sample of Cobalt-60 isotope must be replaced in January 2027
<u>Explanation:</u>
The equation used to calculate rate constant from given half life for first order kinetics:
where,
= half life of the reaction = 5.26 years
Putting values in above equation, we get:
Rate law expression for first order kinetics is given by the equation:
![k=\frac{2.303}{t}\log\frac{[A_o]}{[A]}](https://tex.z-dn.net/?f=k%3D%5Cfrac%7B2.303%7D%7Bt%7D%5Clog%5Cfrac%7B%5BA_o%5D%7D%7B%5BA%5D%7D)
where,
k = rate constant = 
t = time taken for decay process = ? yr
![[A_o]](https://tex.z-dn.net/?f=%5BA_o%5D)
= initial amount of the sample = 100 grams
[A] = amount left after decay process = (100 - 75) = 25 grams
Putting values in above equation, we get:
The original sample was purchased in June 2016
As, June is the 6th month of the year, which means the time period will be 
Adding the time in the original time period, we get:
Hence, the sample of Cobalt-60 isotope must be replaced in January 2027
<span>Kc = [NO2]^4 / [N2O]^2[O2]^3</span>
Pure water may be identified by its density: it will have the lowwest density of the three solutions, given that the solutes (salt and sugar) increase the density (this is the easiests and quickest way).
You can also measure the freezing points or boling points to identify the pure water because the solutes depress the freezing points and increase the boling points.
To differentiate sugar water and salt water, you can probe which one conducts electricity, because salt water is a conductor (given that it ionizes into Na+ and Cl-) but sugar water is not a conductor.
Explanation:
1. subatomic particles.
2.proton, electron and neutron
3.The atomic mass of an element is actually the sum of the MASSES of protons and neutrons in AN atom of that element
4.An element's atomic number is equal to the number of protons in the nuclei of any of its atoms
5. Number of Protons = Atomic Number
Number of Electrons = Number of Protons = Atomic Number
Number of Neutrons = Mass Number - Atomic Number
For krypton:
Number of Protons = Atomic Number = 36
Number of Electrons = Number of Protons = Atomic Number = 36
Number of Neutrons = Mass Number - Atomic Number = 84 - 36 = 48
6. electron, lightest stable subatomic particle known. It carries a negative charge of 1.602176634 × 10−19 coulomb, which is considered the basic unit of electric charge. The rest mass of the electron is 9.1093837015 × 10−31 kg
7.The center of the atom is called a nucleus
8. Negatively charged particles are found in multiple layers outside the nucleus of the atom. These particles are called electrons, and they orbit in various energy levels around the atom's nucleus.
9. A charged particle is also called an ion
