3. how many grams in 18.7 mols of titanium?

895.11 g Titanium

Number of moles, n = Mass, m ÷ relative atomic mass

That is,

n = m ÷ R.A.M.

Therefore, to get the mass we would use, m = n × R.A.M.

In this case,

Number of moles, n = 18.7 moles

R.A.M of titanium = 47.867

Therefore,

Mass of titanium, m = 18.7 moles × 47.867

                                = 895.11 g

Therefore, 18.7 moles of titanium contains 895.11 g

a corroding iron, if that's one of your choices