In order to find the mass (in grams) of an element, you just need to multiply the no. of moles given by the atomic mass of the element, which can be found in a periodic table.
mass of 15.0 moles of N= 15.0 x 14.0 = 210g
mass of 5.0 moles of Zn= 5.0 x 65.4 = 327g
mass of 20.0 moles of H= 20.0 x 1.0 = 20g
mass of 1.0 moles of Pb= 1.0 x 207.2 = 207.2g
Therefore, since 327g is the greatest mass out of the 4 options, the answer is 5.0 moles of Zn.
