To determine mass of the given number of atoms of mercury, we need a factor that would relate the number of atoms to number of moles. In this case, we use the Avogadro's number. It is a <span>number that represents the
number of units in one mole of any substance. This has the value of 6.022 x
10^23 units / mole. The number of units could be atoms, molecules, ions or electrons. To convert into mass, we use the given amu of mercury since it is equal to grams per mole. We calculate as follows:
</span>3.0 x 10^10 atoms ( 1 mol / 6.022 x 10^23 atoms ) ( 200.59 g / 1 mol ) = 9.99x10^-12 g Hg
We are given the chemical reaction and the amount of reactant used for the process. We use these data together to obtain what is asked. We do as as follows:
0.882 mol H2O2 ( 1 mol O2 / 2 mol H2O2 ) = 0.441 mol O2 produced
Hope this answers the question.
Answer:

Explanation:
Given,
The density of Helium is 
We need to find the density in Dg/μm
We know that,
1 g = 10 dg
1 cm³ = 10¹² μm³
So,

So, the density of Helium is equal to
.
A compound contains atoms of different elements chemically combined together in a fixed ratio. An element is a pure chemical substance made of same type of atom. Compounds contain different elements in a fixed ratio arranged in a defined manner through chemical bonds.