Balance the three copper reactions: i) Cu(s) + HNO 3 (aq) -> Cu(NO 3 ) 2 (aq) +

Question

Balance the three copper reactions: i)   Cu(s) + HNO3(aq)               ->   Cu(NO3)2(aq) + NO2(g) + H2O(l) ii)  Cu(NO3)2(aq) + NaOH(aq) ->  Cu(OH)2(s) + NaNO3(aq) iii) Cu(OH)2(s)                             -> CuO(s)   + H2O(l) Q #1) In reaction (i) suppose that you add 12.8mL of 6M nitricacid to a sphere of copper metal thaat weighs 1.06 grams. Whichreactant is the limiting reagent? (show work) Q #2) a. Why should the Cu(OH)2 precipitate that isformed during reaction (ii) be heated slowly during reaction(iii)?           b. Whydoes reaction (i) have to be carried our in the fume hood? Balance the three copper reactions: i)   Cu(s) + HNO3(aq)               ->   Cu(NO3)2(aq) + NO2(g) + H2O(l) ii)  Cu(NO3)2(aq) + NaOH(aq) ->  Cu(OH)2(s) + NaNO3(aq) iii) Cu(OH)2(s)                             -> CuO(s)   + H2O(l) Q #1) In reaction (i) suppose that you add 12.8mL of 6M nitricacid to a sphere of copper metal thaat weighs 1.06 grams. Whichreactant is the limiting reagent? (show work) Q #2) a. Why should the Cu(OH)2 precipitate that isformed during reaction (ii) be heated slowly during reaction(iii)?           b. Whydoes reaction (i) have to be carried our in the fume hood?

Explanation / Answer

We Know that : i )        Cu    +   4HNO3  --------> Cu (NO3)2 + 2 NO2 + 2 H2O ii )          Cu (NO3)2 + 2 NaOH  --------> Cu ( OH )2 + 2NaNO3 iii)           Cu ( OH)2   -------> CuO + H2O 1.              From the above equations it is clear that :               1 mole of copper reacts with 4 moles of HNO3             Number of moles of HNO3 is 6M x0.0128 = 0.0768 moles              Number of moles of Cu taken = 1.06 gm / 63.54 gm / mole                                                               = 0.0166 mole    From the above the moles of Cu andHNO3 it is clear that Cu acts as limitingreagent.         Cu(OH)2 precipitate is heated slowly to remove thewater molecules from it but if we heat vigorously we get       solid residue of CuOwhich is red solid mass so their is a loss of copper during theprocess.           The fuming HNO3 is very injurious the vapours leadto suffocating odour so the Reaction has to be carriedat           fume hood chamber.                  iii)           Cu ( OH)2   -------> CuO + H2O 1.              From the above equations it is clear that :               1 mole of copper reacts with 4 moles of HNO3             Number of moles of HNO3 is 6M x0.0128 = 0.0768 moles              Number of moles of Cu taken = 1.06 gm / 63.54 gm / mole                                                               = 0.0166 mole    From the above the moles of Cu andHNO3 it is clear that Cu acts as limitingreagent.         Cu(OH)2 precipitate is heated slowly to remove thewater molecules from it but if we heat vigorously we get       solid residue of CuOwhich is red solid mass so their is a loss of copper during theprocess.           The fuming HNO3 is very injurious the vapours leadto suffocating odour so the Reaction has to be carriedat           fume hood chamber.                 

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