Question

The mass of a an atom of helium is 6.65 x 10^−24. Use scientific notation to express the mass of 250 helium atoms.

Answer 1

i took the test and it's actually A) 1.6625 x 10−21 :)

Answer 2

1.6625 x 10−21

mass of one helium atom x 250 
Express 250 as 2.50.
(6.65 x 10−24)(2.50 x 102)
16.625 x 10−22