Chemical formula and thoretical/percent yield.

[lvlastermind]

Main Question or Discussion Point

2 ml of 15M Nitric acid was added to copper bromide(CuBr) and gently heated untill a black substance was formed, copper oxide(CuO), and was completly dry. There was .93g of CuO formed in the reaction. The CuO was formed from the decomposition of the copper nitrate produced by the reaction of ntitric acid with copper bromide.

I have to find the chemical formula and calculate the theoretical and percent yields.

I'm having trouble writing the chemical formula...So far i have
CuBr + HNO3 ----> CuNO3 + Br2 + H2
(I know its not balanced yet but i want to know if its right before i balance it)

and

CuNO3 + HNO3 ----> CuO + N2
(This also isnt balanced)


Do i have to combine these formulas to find a formula that models the reaction? If so, how do I do that?

 

[Borek]

Are you sure you start with copper (I) bromide, and not with copper (II) bromide? If the copper is oxidized yield will be unpredictable, as nitric acid can be reduced to both NO₂ and NO during reaction, thus stoichiometry will be dubious.

 

[lvlastermind]

im fairly confident that it is copper (I) bromide

 

[Borek]

Nitric acid is highly concentrated so you may assume that it is reduced to NO₂ when dissolving CuBr. First step will be to priduce copper (II) nitratne, second will be decomposition to CuO. Note that in the second step reaction equation is not as important as in the first step.

 

[lvlastermind]

thanks for the help :)