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
Answer:
a. Al2S3.
Explanation:
Molar mass of Al = 26.98
Molar mass of S = 32.06.
Ratio of AL:S is 1 : 1.78
Dividing by the moles we get:
0.0371 : 0.0555
= 1 : 1.5
So its Al2S3.
Answer:
when cell is exposed to radiation we get brain tumour or cancer.
Answer:
B.
Explanation:
There are the same amount of black circles in the reactant and product. There are also the same amount of white circles in the product and reactant.
Answer:mirror
Explanations: A lens is a piece of a glass or other transparent substance with curved sides for concentrating , dispersing light rays used singly as in magnifying glass or with lenses therefore mirror doesn’t have lenses but telescope microscope and eyeglasses have
