Below is an experiment and some questions follow: Step 1) Cu (s) + 4 HNO3 -> Cu^
ID: 966077 • Letter: B
Question
Below is an experiment and some questions follow:
Step 1)
Cu (s) + 4 HNO3 -> Cu^(2+) + 2 NO3^(-) + 2 NO2 + 2 H2O
Cu^(2+) + 6 H2O -> Cu(H2O)6 &^(2+)
Description: Weight .49 of Cu wire and record . Under the heat add roughly 5 ML HNO3(nitric acid). When CU is dissolved add 10 mL of DI H2O.
Step2)
Cu(H2O)6 &^(2+) + 2 NaOH -> Cu(OH)3 + 6 H2O
Description: Add 6 MNaOH drop wise while stirring. Stop when litmus paper turns blue.
Step3)
Cu(OH)3 ->(heat) CuO + H2O
Description: Add 80 90 mL DI H2O Ba gently white string for 4 min. Allow to cool and vacuum filter precipitate. Wash with 5 mL hot water 3 times. Use 250 mL vacuum flask. Discard filtrate.
Step4)
CuO + H2SO4 -> Cu(H2O)^2+
Description: Dissolve CuO with 10 mL 3 MH2SO4. If not dissolved wash with filtrate again. Wash filter paper with DI H2O and collect in filtrate.
Step5)
Cu(H2O)6 ^(2+) + Zn -> Cu + Zn ^(2+)+ + 6 H2O
Description: Add .5 g of Zn and stir occasionally. Reaction is complete when all Zn is dissolved and solution is colorless.
Wash 4 times with 20 mL DI H2O.
Weight watch glass and 2 pieces of filter paper vacuum filter Cu solid.
Transfer Cu + fitler paper to watch glass.
Dry in Oven. Then Weigh.
Questions 1:
When performing part 5 of the experiement,
A student used equation 7( CU(H20)6 ^(2+) + Zn -> Cu + Zn^(2+) + 6H2O ).
to caluclate the precises math of zinc needed to reduce the copper hexahydrate( Cu(H2O)6 ^(2+) ions in his solution.
His calculated % recoever of copper was very low. Brefly explain what might account for his lower recoever of copper?
Question 2:
What would happen if the yield of copper if the temp of the over is over 150 degrees C?
Explanation / Answer
ANSWER
1.The Cu(H2O)6 ^2+ is obtained from a series of reaction, at each step the student may end up with smaller product than expected. Further Cu(H2O)6 2+ may contain imurities of other substances.
2. The yield may be increases becuase the moisture may be completely removed.
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