Part 1: Synthesis of Copper(II) Nitrate and Copper(II) Hydroxide
Cu(s) + 4HNO3(aq) Cu(NO3)2(aq) + 2NO2(aq) + 2H2O(l) * Redox reaction Reducing reagent=Cu and Oxidizing reagent=HNO3 * Copper and 10mL of concentrated nitric acid (HNO3) * reaction carried out in the fume hood, brown gas given off * swirl the reaction mixture to remove any gases trapped in the solution * solution changed from green to blue * It is SPONTANEOUS (heat is given off)
Cu(NO3)2(aq) + 2NaOH(aq) Cu(OH)2(s) + 2NaNO3(aq) * Double displacement reaction * Dilute above solution with 25 mL deionized water * Stir and add 25 mL of %20 Sodium Hydroxide (OH) * It is SPONTANEOUS * The solution should be basic (alkaline) after the addition * Cu(OH)2, the product, is a gelatinous precipitate * Cu(OH)2, the product, is blue
Part 2: Synthesis of Copper(II) Oxide
Cu(OH)2(s) +(heat) CuO(s) + H2O(l) * Decomposition reaction by heat * During heating stir to avoid bumping/spattering * Heat until boiling point is reaction * Copper to be recovered changes from Cu(OH)2 to CuO * CuO is less gelatinous precipitate than Cu(OH)2 is, thus easier to isolate * The blue Cu(OH)2 becomes black CuO * If heating doesn't do the trick we add MORE NaOH * Vacuum Filtration * Filter with a suction filter flask and a Buchner funnel * Wash the CuO with water: 1) to get it out of the beaker 2) CuO is wet with a solution, contains NaNO3 and NaOH (by washing it we replace this solution with water)
Part 3: Synthesis of Copper (II) Sulfate
CuO + H2SO4 + (heat) CuSO4(aq) + H2O(l) * 20 mL of 3M Sulphuric acid is used (heating is used as well) * CuSO4 is water soluble * As the CuSO4 forms Cu2+ ion gets hydrated to become Cu(H2O)42+ * The BLACK CuO will dissolve into a blue solution * Crystalline compound won’t be isolated but converted to Cu * If black CuO doesn’t dissolve completely, heat solution * If insoluble residue remains add CuSO4 * Double displacement reaction Part 4: Synthesis of Copper
CuSO4(aq) + Zn(S) ZnSO4(aq) + Cu(s) * Redox reaction- Reducing reagent=Zn and Oxidizing reagent= Cu * Add zinc to blue CuSO4 * Zinc is more chemically active than copper and displaces copper(II) ions from solutions, meaning that it is better at combining with SO4 than Cu * the blue solution will turn white/clear * Solid visible consists of unreacted zinc metal and copper metal (products) * In fume hood add 10 mL of 6M HCl to dissolve the zinc * Spontaneous
Zn + 2HCl -> ZnCl2 + H2 * Redox reaction (spontaneous)- Reducing reagent=Zn and Oxidizing reagent= HCl * Removes excess zinc * Reaction is over when there is no more bubbles (no formation of H) * Zn and HCl are supernatant thus discard * Heat Cu to evaporate liquid/allow to air dry then weigh
Formula for % yield: Formula For % recovery:
Error 1: Spattering while boiling/inadequate quantitative transfer/spilling of product
Result: loss of copper-loss of mass (lower % yield/recovery)
Error 2: Incomplete drying/purification (sanding and washing)/incomplete reactions involving Zn and HCl
Result: Addition of mass (higher % yield/recovery)
Bumping: Boiling a solution causes big bubble to form and force liquid out of flask.
Quantitative transfer: transfer all material/product from one container to another without loss.
Decant: Separate a supernatant from solid by gradually pouring out supernatant from one container to another without disturbing pellet.
Supernatant: Liquid above sentiment of precipitate.
Questions to Understand. 1. In part 1, after the copper was dissolved, 25 mL of 20% NaOH was slowly added to the solution. Why is it important to make this addition slowly? * To avoid oxidizing the solution