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Chemistry gcse question- I don’t understand it

A sample of a substance has 1.204*10 to the 25 atoms. How many moles of atoms of the element are there?
We do 1.204*10to the power of 25 divided by Avogadro constant to get 20 moles which is definitely right
B) given that the atoms have a mean mass of 9.3*10 to the power of -23 grams. What is the element?
So I was wandering if mass/ moles = mass number then surely we have to do 9.3*10 to the power of -23 grams/ by the 20 moles from part a? But the answer isn’t correct. Please try to explain it for me too

Reply 1

DraconisAudiat

Avogadro Constant is the number of atoms in one mole.

One mole is the same number of grams as the molecular mass or atomic mass.

a) You have 1.204*10*25 atoms

Avogadro's constant is 6.022*10^23

1.204*10*25 atoms / 6.022*10^23 avogadro = 20 moles

Section B I don't follow you, is it possible you did a typo and it's ^23 not ^-23?
When it says "the atoms have a mean mass" do you mean "this particular sample of atoms" or "a specific amount [1 mole, 1 unit volume] of atoms"?