If your lab partner needed 1.936 x 1021 molecules of magnesium fluoride (mgf2), how many milligrams would you need to weigh out?

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!

Answer-ide.