Chemical Forums
Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: renots on February 13, 2006, 11:44:50 AM
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sry i cant figure the answer to this problem out and its due b4 my lab in like 2 hrs
Write the balanced chemical equation for the reaction of Cu(NO3)2 (aq) with KI (aq) including states. Note: Two of the products are CuI and I2. Which of the above reactants change oxidation states? What are the changes?
if anyone could help i would greatly appreciate it.
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Cu2+ + I- -> CuI + I2
This is not balanced, but that's relatively easy (note: charge must be balanced as well as atoms). Write oxidation numbers near all ions/atoms - which ones are changing?
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what happens to the K and the NO? do they get used up or something?
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K+ is just a spectator ion, but if you must you can think of KNO3 being formed, but its not accurate way to think.
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Cu(NO3)2 + KI -----> CuI + I2 + X
would the X be kno3, and how would i balance that? could i take the kno3 completely out of the equation? when im balancing i just end up going in a never ending circle of increasing coefficiencts
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This is a quite easy redox reaction, which can be split into two steps. The fiirst one is a double exchange reaction
Cu(NO3)2 + 2KI = CuI2 + 2KNO3
The next step is a redox one
2CuI2 = 2CuI + I2
After joining both reaction together (with proper coefficients):
2Cu(NO3)2 + 4KI =
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2CuI2 = 2CuI + I2
Interesting thing is that this reaction equilibrium is driven by low CuI solubility. Comparison of potentials of both half-reactions (Cu2+/Cu+, I2/I-) suggests that no redox reaction should take place.