As a purchasing agent for a pharmaceutical company, how much chlorine, cl2, do you need to order to react completely with 500 kg of platinum, pt, to make cisplatin, ptcl2(nh3)2?

The formula tells you the proportion in mols

2 mols of Cl: 1 mol of Pt

Now use the atomic masses:

Cl: 35.5 g/mol
Pt: 195 g/mol

Then you have these equation:

[2*35.5 g Cl] / 195 g Pt = x / 500 kg Pt

Solve for x.

x = (71 g Cl / 195 g Pt) * 500 kg Pt

x = 182 Kg Cl = 182 kg Cl2.

Ci hope  it  you