Answer:
B no observation pls mark me branilest
Answer:

Explanation:
Given that:
The Half-life of
=
is less than that of 
Although we are not given any value about the present weight of
.
So, consider the present weight in the percentage of
to be y%
Then, the time elapsed to get the present weight of
= 
Therefore;

here;
= Number of radioactive atoms relating to the weight of y of 
Thus:

--- (1)
However, Suppose the time elapsed from the initial stage to arrive at the weight of the percentage of
to be = 
Then:
---- (2)
here;
= Number of radioactive atoms of
relating to 3.0 a/o weight
Now, equating equation (1) and (2) together, we have:

replacing the half-life of
=
( since
)
∴

The time elapsed signifies how long the isotopic abundance of 235U equal to 3.0 a/o
Thus, The time elapsed is 
Answer:
a. V = 1000 mL
b. Denisty = 0.022 g/mL
Explanation:
a.
First we need to convert the volume of the Osmium into mL. For that purpose we are given the conversion unit as:
1 mL = 0.1 cL
Hence, the given volume of Osmium will be:
V = Volume of Osmium = 100 cL = (100 cL)(1 mL/0.1 cL) = 1000 mL
<u>V = 1000 mL</u>
b.
The density of Osmium is given by the following formula:
Density = mass/Volume
Denisty = 22 g/1000 mL
<u>Denisty = 0.022 g/mL</u>
<span>C6H12 = 6x12 + 6x1 = 78.
The equation indicates that 2x78 = 156g benzene will produce 6542kJ.
Using proportions you can then calculate that
x/6542kJ = 7.9g / 156g
x = 331.3kJ = 331300J.
heat = mass x ΔT x 4.18J/g°
ΔT = 331300J / (5691g x 4.18J/g°) = 13.9°
final temp = 21 + 14° = 35°C</span>