Answer:
Gravity explains this.
Explanation:
Weights and mass are different terms .
Weight is defined as the force exerting on the surface due to the mass and gravity of acceleration.

Here mass is related to the density of the body. So as the density would be same mass woulnt vary.
Whereas the Gravity changes due to the property of the planet.
Gravity is different for different planets and hence moon and earth have two different values.
So the mass i.e density remains same on both planets but the g value always changes hence weight is different.
The given question is incorrect. The correct question is as follows.
If 20.0 g of
and 4.4 g of
are placed in a 5.00 L container at
, what is the pressure of this mixture of gases?
Explanation:
As we know that number of moles equal to the mass of substance divided by its molar mass.
Mathematically, No. of moles = 
Hence, we will calculate the moles of oxygen as follows.
No. of moles = 
Moles of
=
= 0.625 moles
Now, moles of 
= 0.1 moles
Therefore, total number of moles present are as follows.
Total moles = moles of
+ moles of 
= 0.625 + 0.1
= 0.725 moles
And, total temperature will be:
T = (21 + 273) K = 294 K
According to ideal gas equation,
PV = nRT
Now, putting the given values into the above formula as follows.
P =
= 
=
atm
= 3.498 atm
or, = 3.50 atm (approx)
Therefore, we can conclude that the pressure of this mixture of gases is 3.50 atm.
I had to look for the options and here is my answer:
The two requirements for nuclear fusion that are needed to be met in order for the elements hydrogen and helium fuse to make heavier elements are extremely high temperatures and density. Hope this helps.