the reaction between Cu and HNO3 is clearly unusual. But is my explanation and understanding for why they react correct"the HNO3 is an oxidizing agent thus turning Cu to Cu2O. In the form of copper oxide, the reaction between Cu and HNO3 will happen?"--if it is wrong may someone please explain why the reaction occurs
Hi John: The reduction potential for Cu (+0.34 V) is above that for H2 (0.00 V) and so copper will NEVER displace H2 from dil HNO3 (I've seen several times on this forum views to the contrary). Conc acids however have a whole different chemistry to dil strong acids. In very conc HNO3 (i.e., 100%) Cu is passive for reasons not understood but may be due to a protective CuO coating being formed. In conc HNO3 it is a strong oxidizing acid. I knew the rxns of Cu with somewhat less conc HNO3, but after looking in my texts the conc was only given for the NO production (C&W) [1]. Then I recalled seeing a video of Cu and conc nitric and here it is [2] with equations: Cu(s) + 4HNO3(aq) ——> Cu(NO3)2(aq) + 2NO2(g) + 2H2O(l) They are obviously using commercial conc HNO3 (~70%, ~16M). In the next exp they say dilute HNO3 but that isn't true (C&W says 8M HNO3) which I recall is about right. 3Cu(s) + 8HNO3(aq) ——> 3Cu(NO3)2(aq) + 2NO(g) + 4H2O(l) Well there's another one solved! Cheers, drp
