Question

What is the maximum mass of CuS which can be formed when 38.0 mL of 0.5 M CuCl2 are mixed with 42.0 mL of 0.6 M
(NH4)2S? Aqueous ammonium chloride is the other product.

Answer 1

It's a limiting reactant problem, so you have to check the moles!

First turn everything into moles:
M=mol so mol=M X L(or in this case mL x 1000)
---
L

then once you have moles, multiply them with the balanced eqtn to see how many moles of CuS you can make with each amount. The LEAST moles is the limiting reactant, then just convert to mass!