Data:
Arsenic Molar Mass = 74,9216 ≈ 75 u (atomic mass unit)
Solving:
1 mole of arsenic → 75g ------------ 6,0210²³ molecules
..................................X -------------- 1 molecule
6,0210²³X = 75
\(x = \frac{75}{6,02*10^{23}}\)
\(\boxed{x \approx 1,24*10^{24}grams}\)
