Question

How many atoms of gold (Au) are present in a sample of 2.5 mol Au?

1.5 × 1024 atoms Au

1.5 × 1023 atoms Au

4.2 × 1024 atoms Au

4.2 × 1023 atoms Au

Answer 1

There are 6.02*10^23 atoms per mole (avogadro's constant). So 2.5*avogadro's constant will give you the answer!

Answer 2

You can check your answer on Wolfram
http://www.wolframalpha.com/input/?i=atoms+in+2.5+mol+Au