Question

how many atoms are their in 100 amu of He

Answer 1

hi friends

mass of one atom of helium (He) = 4 amu(atomic mass unit)
100 amu of He = 100/4 = 25 
So, 25 atoms are there in 100 amu of He.

thank you 

Answer 2

Explanation:

The term amu and grams are equivalent to each other. So, it is given that mass of helium is 100 g and atomic mass of helium is 4.

Therefore, first calculate the moles as follows.

              Number of moles = $\frac{mass}{molar mass}$

                                            = $\frac{100 g}{4 g/mol}$

                                            = 25 mol

Now, number of atoms present in 100 g of He are as follows.

                         $25 mol \times 6.022 \times 10^{23} atoms/mol$

                        = $150.55 \times 10^{23}$ atoms

Hence, we can conclude that there are  $150.55 \times 10^{23}$ atoms in 100 g of He.