Molar mass MgF₂ = 62.3018 g/mol
Use avogrado's constant:
62.3018 g ---------------- 6.02x10²³ molecules
mass MgF₂ -------------1.936x10²¹ molecules
mass MgF₂ = ( 1.936x10²¹) x ( 62.3018 ) / 6.02x10²³
mass MgF₂ = 1.206x10²³ / 6.02x10²³
=> 0.2003 g
Therefore:
1 g ----------- 1000 mg
0.2003 g ------- ?
0.2003 x 1000 / 1 => 200.3 mg of MgF₂
hope this helps!
