J.R. S. answered 03/11/19
Ph.D. University Professor with 10+ years Tutoring Experience
The excess acid would be 2 ml of 16 M HNO3 assuming the 4.0 ml of acid was the exact amount needed for 0.18 g of Cu. You can do tge calculations to determine this. 0.18 g Cu / atomic mass Cu = moles Cu. Is this = to moles acid using 4 ml of of 16 M acid?
moles HNO3 = 0.002 L x 16 mol/L = 0.032 moles in excess
(xL)(6.0 mol/L) = 0.032 mol
x = 0.00533 liters = 5.33 mls of NaOH