2. Because the student added too much nitric acid, he attempted to compensate by
ID: 537507 • Letter: 2
Question
2. Because the student added too much nitric acid, he attempted to compensate by adding more sodium hydroxide, as well. He added 20.0mL of 6.0M NaoH. Was this enough sodium hydroxide to neutralize the excess nitric acid after the copper reaction from the question above? 3. Would you expect litmus paper to be red or blue, if adding the amount of NaoH from question 2 to the copper and nitric acid reaction mixture in the laboratory procedure? Based on this litmus paper result, what is the appropriate action to complete step 2 of this laboratory? 4. What would the solution look like after adding 20.0 mL of 6.0M NaoH described in question 2? Describe the color of the solution and state ifany precipitate will be present. You may need to consult your observations from the laboratory to answer this question. 5. What would be the effect on the percentage recovery if not enough NaOH was added in Step 2 to react with both the unreacted HNO3 and the Cu that are present at the end of Step 1? Explain your answer. 6. Given a solution containing a tin salt, would you be able to recover the tin its elemental form? Please discuss your answer. Consult the activity series in Chapter 4 of your text. REFERENCES: Roberts, Hollenberg, Postma, General Chemistry in the Laboratory (pp. 67-74), modified by the ARC Chemistry Department Condike, G.F., J Chem. Educ. 52:615, 1975
Explanation / Answer
5.If sufficient sodium hydroxide is not added in step 2 then excess nitric acid will make the solution acidic and litmus colour will be red and so the blue colour of Copper nitrate can't be seen. So percentage recovery will be less.
6.In electrochemical series Sn is present just above On with an electrode potential of -0.14 V
It's more electropositive than hydrogen.
So if aqueous solution of Sn is used for electrolysis then instead of Sn Hydrogen gas will be obtained at cathode.
But Sn can be displaced by other more electropositive metal like Zn, Mg, All which are above than Sn in electrochemical series.
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