First, let's see the proportion of the chemical equation:
8 moles of HNO₃ need to react with 3 moles of Cu.
You have 2.0 mol of HNO₃, so you can use the rule of 3 to find out how many moles of Cu you will need.
8 moles of HNO₃ ----- 3 moles of Cu
2 moles of HNO₃ ----- x moles of Cu
8x = 3 × 2
x = 6/8
x = 0.75 moles of Cu.
But you need to find how many grams. To find out, you need to know what the atomic mass of Cu. You can consult the periodic table to find out, the atomic mass of copper is 63.6 g/mol.
Now you need to transform moles into grams:
63.6 g of Cu ---- 1 mol of Cu
x g of Cu ---- 0.75 mol of Cu
x = 63.6 × 0.75
x = 47.7 g
Answer: It is needed 48 g of Cu to react with 2.0 mol of HNO₃.