Question

A sample of C3H8 has 6.72 x 10^24 H atoms.
What is the total mass of the sample?

Answer 1

number if atoms can be found by
number if moles * (6.02*10^23)= number of atoms

p.s. 6.02*10^23 is Avogadro number

so using this formula you can find number of moles of H atoms
number of moles= number of atoms/ (6.02*10^23)

Answer 2

C3H8
you got mole of H atoms in this compound
now find mole of the whole compound

molecular mass of ALL H atoms in C3H8 (use periodic table) - mole of H atoms in C3H8 that you just got
molecular mass of C3H8 (use periodic table)- X moles of C3H8
so
X= molecular mass of C3H8 * mole of H atoms / molecular mass of H atoms in C3H8

so
now you found mole of C3H8

Answer 3

mole= mass/ molecular mass
so
mass= mole C3H8 * molecular mass of C3H8
so get the mass
i hope it was clear :)

Answer 4

thanks

Answer 5

no problem :3