A sample of He - gas has 5.03 x 10 23He atoms. What volume is occupied by this sample at s. t.p?

18.7L

Explanation:

To solve this problem, we first find the number of moles the given number of atoms of He represents.

  Number of atoms of He  = 5.03 x 10²³ atoms

So;

           6.02  x 10²³ atoms will contain 1 mole of He

          5.03 x 10²³ atoms  will have   = 0.84mole of He

Now, the volume at STP;

          1 mole of He will occupy 22.4L at STP

          0.84 mole of He will occupy 0.84 x 22.4  = 18.7L at STP

the correct answer would be d. hope this !