Answer : The initial temperature of system 2 is, 
Explanation :
In this problem we assumed that the total energy of the combined systems remains constant.
The mass remains same.
where,
= heat capacity of system 1 = 19.9 J/mole.K
= heat capacity of system 2 = 28.2 J/mole.K
= final temperature of system = 
= initial temperature of system 1 = 
= initial temperature of system 2 = ?
Now put all the given values in the above formula, we get
Therefore, the initial temperature of system 2 is,
Answer:
a mixture of molecules - Box f
atoms of a pure elementa metal - Box D
a solid compound - Box C
a mixture of elements - Box A
Explanation:
Box a has mixture of elements which forms a solid like shape but there are different elements present in the box. The box f has mixture of molecules in which many atoms are combined together. Box c has solid compound with single element.
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% .
.
Note : Because Many of My Dreams came true and I realized.
Answer:
you must go to jones im doing the same test
Explanation:
