posted by Mima on .
Why the addition of NH3 should be precise in spectrophotometer reading? What if it gives darker color?
NH3 in what? darker color than what? What experiment are you doing? Details?
Spectrophotometer. 2 ml of NH3 is added to Cu(NO3)2 to give it dark blue color. If we accidantely put 3 ml of NH3, would the absorbance reading by spec should be considered? Explain.
I wrote we shouldn't consider the reading because it will give darker color than it should be and the reading would be beyond the expected range. Is that right?
You don't have all of the experimental details written for me; however, my best guess is that the NH3 is not the limiting reagent. That is, I suspect that the experiment is to eventually determine Cu and adding NH3 gives the dark blue color. If I'm right about that then 2 mL NH3 is enough to complex ALL of the Cu ion and still have NH3 left over. I don't know the total volume but I don't think 1 mL out of several will make too much difference except for the dilution. It won't make it darker but it could dilute it enough to be a little less intense color.