Answer:- The natural abundance of 
is 0.478 or 47.8% and 
is 0.522 or 52.2% .
Solution:- Average atomic mass of an element is calculated from the atomic masses of it's isotopes and their abundances using the formula:
Average atomic mass = mass of first isotope(abundance) + mass of second isotope(abundance)
We have been given with atomic masses for and as 150.919860 and 152.921243 amu, respectively. Average atomic mass of Eu is 151.964 amu.
Sum of natural abundances of isotopes of an element is always 1. If we assume the abundance of as n then the abundance of would be 1-n .
Let's plug in the values in the formula:
151.964=150.919860n+152.921243-152.921243n
on keeping similar terms on same side:
negative sign is on both sides so it is canceled:
The abundance of is 0.478 which is 47.8%.
The abundance of is = 
= 0.522 which is 52.2%
Hence, the natural abundance of is 0.478 or 47.8% and is 0.522 or 52.2% .
Radio waves have the lowest energy, but the longest wavelength. So radio waves is the answer. Good luck on the rest and message me for more help.
Answer:
B
Explanation:
A chemical reaction equation is balanced if the number of atoms of each element on the right hand side of the reaction equation is the same as the number of atoms of the same element on the left hand side of the reaction equation.
By inspection, the chemical reaction written in the question is a balanced chemical reaction equation.
However, the statement in option B that more molecules of N2 are needed to produce NH3 than molecules of H2 is a false statement since only one mole of N2 and three moles of H2 are required to produce NH3 according to the reaction equation as written in the question.
Answer : The mass of chlorine reacted with the phosphorus is, 53.25 grams.
Explanation :
First we have to calculate the moles of phosphorus.
Now we have to calculate the moles of 
The balanced chemical reaction is:
From the balanced chemical reaction, we conclude that
As, 2 moles of phosphorous react with 3 moles of
So, 0.5 moles of phosphorous react with 
moles of
Now we have to calculate the mass of
Molar mass of = 71 g/mol
Therefore, the mass of chlorine reacted with the phosphorus is, 53.25 grams.
The answer is B. uniform in composition.
