I believe the answer you are looking for is : SHORT
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% .
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Ability to move up through thin tunes because a physical property is something you can observe about the matter. Out of all of them this one does not fit.
To
determine the volume of both concentration of the solution to make another concentration of solution, we need to set up
two equations since we have two unknowns. <span>
For the first equation, we do a mass balance:
mass of 50% solution + mass of 20% solution =
mass of 40% solution
M1 + M2 = M3
For the second equation, we do a component balance,</span>
<span>
M1(50%) + M2(20%) = M3(40%)
.50M1 + .20M2 = .40M3
To determine the ratio, we assume we have to make a 100 g of the 40% solution. So, the equation would change to</span>
<span>
</span>
<span>M1 + M2 = 100</span>
.50M1 + .20M2 = (100)(.40) = 40
Solving for M1 and M2,
M1 = 66.67 g
M2 = 33.33 g
So, the ratio of the 20% and the 50% would be approximately 33.33/66.67 = 0.5.
