Which of the following would have the greatest mass?

15.0 moles of N

20.0 moles of H

5.0 moles of Zn

1.0 moles of Pb

5.0 moles of Zn

when you convert all of them into grams you'll find that Zn has the greatest mass

5.0 moles of Zn.

Explanation:

From the molar masses we get 15 moles of N = 15 * 14 = 210 g.

20 moles of H = 20.16 g,

5 moles of Zn = 5*65.38 = 326.9 g.

1 mole of lead = 207.2 g.