You need 0.111 g of NH₃ to provide the same number of molecules as
in 0.95 g of SF₆.
Step 1. Convert grams of SF₆ to moles of SF₆
Moles of SF₆ = 0.95 g SF₆ × (1 mol SF₆/146.06 g SF₆) = 0.006 50 mol SF₆
Now, we can use the knowledge that 1 mol of anything has the same number of molecules (Avogadro’s number) as 1 mol of anything else .
Thus, 0.006 50 mol NH₃ has the same number of molecules
as 0.006 50 mol SF₆.
Step 2. Convert moles of NH₃ to grams of NH₃.
Mass of NH₃ = 0.006 50 mol NH₃ × (17.03 g NH₃/1 mol NH₃) = 0.111 g NH₃