Answer:
2.1x10⁹ years
Explanation:
U-238 is a radioactive substance, which decays in radioactive particles. It means that this substance will lose mass, and will form another compound, the Pb-206.
The time need for a compound loses half of its mass is called half-life, and knowing the initial mass (mi) and the final mass (m) the number of half-lives passed (n) can be found by:
m = mi/2ⁿ
The mass of Pb-206 will be the mass that was lost by U-238, so it will be mi - m. Thus, the mass ration can be expressed as:
(mi-m)/m = 0.337/1
mi - m = 0.337m
mi = 1.337m
Substituing mi in the expression of half-life:
m = 1.337m/2ⁿ
2ⁿ = 1.337m/m
2ⁿ = 1.337
ln(2ⁿ) = ln(1.337)
n*ln(2) = ln(1.337)
n = ln(1.337)/ln2
n = 0.4190
The time passed (t), or the age of the sample, is the half-life time multiplied by n:
t = 4.5x10⁹ * 0.4190
t = 1.88x10⁹ ≅ 2.1x10⁹ years
<u>Answer:</u> The given isotope of tin has 50 protons and 69 neutrons.
<u>Explanation:</u>
Atomic number is defined as the number of protons or number of electrons that are present in neutral atom. It is represented as Z.
Atomic number = Number of protons = Number of electrons
Mass number is defined as the sum of number of protons and number of neutrons. It is represented as A.
Mass number = Number of protons + Number of neutrons
We are given:
An isotope having representation 
Mass number of Sn = 19
Atomic number = 50
Number of neutrons = Mass number - Atomic number = 119 - 50 = 69
Hence, the given isotope of tin has 50 protons and 69 neutrons.
Answer:
defined as a process in which mo heat transfer take place
Explanation:
is a process which occurs without transferring heat /mass between the system and it's surrounding.
<u>Answer:</u> The molality of magnesium chloride is 1.58 m
<u>Explanation:</u>
To calculate the molality of solution, we use the equation:
Where,
= Given mass of solute (magnesium chloride) = 75.0
= Molar mass of solute (magnesium chloride) = 95.21 g/mol
= Mass of solvent = 500.0 g
Putting values in above equation, we get:
Hence, the molality of magnesium chloride is 1.58 m
The correct answer is D:
it involves breaking molecular bonds between copper compounds
.
The explanation :
-when we melt a copper it is a physical change because the substance is still copper and have the same shape.
- but for example Burning a copper it is a chemical change. Fire activates a chemical reaction between copper and oxygen.
-The oxygen in the air reacts with the copper and the chemical bonds are broken.
- the chemical change is changing the other compound bonded to the copper atoms.
So, the correct answer is D
