Nick needs 3.5 moles of sodium fluoride (NaF) for a solution he is mixing in the lab. How many grams of NaF does Nick need to measure out?

147 g

Explanation:

The number of moles of a substance is the ratio of the mass of the substance and the molar mass of that substance. Mathematically,

  mole = mass of substance/molar mass

In this case, Nick needs 3.5 moles of NaF, the molar mass of NaF is calculated as:

  23 + 19 = 42 g/mol (Note: Na = 23, F = 19)

Hence,

mass of 3.5 mole NaF = mole x molar mass

                              = 3.5 x 42 = 147 g.

Hence, Nick would need to measure out 147 g NaF using a suitable weighing balance.