How do I solve this Chemistry problem?

Question

How many mL of 2.50M HNO3 contain enough nitric acid to dissolve an old copper penny with a mass of 3.94 grams?

 

The equation for this reaction is:

 

3Cu (s)+ 8HNO3 (aq)===> 3Cu (NO3)2 (aq)+ 2NO (g)+ 4H2O

Answer 1

3Cu (s)+ 8HNO₃ (aq)===> 3Cu (NO3)₂ (aq)+ 2NO (g)+ 4H₂O  ... Balanced Equation

First, find the moles of Cu present.  Next, from the balanced equation, find the moles of HNO3 required.  Finally, calculate the volume HNO3 that contains that many moles.

(1) moles Cu present = 3.94 g Cu x 1 mole Cu/65.5 g = 0.0602 moles Cu

(2) from balanced equation, 3 moles Cu require 8 moles HNO3.

moles HNO₃ required = 0.0602 moles Cu x 8 moles HNO₃/3 moles Cu = 0.161 moles HNO3 required

(3) volume of HNO₃ = 0.161 moles HNO₃ x 1 liter/2.50 moles HNO₃ = 0.0644 liters = 64.4 ml HNO₃