Suppose that you start with .303g of copper wire and faithfully follow the procedure. at the end you find that the copper dust weighs .309g. base on your understanding of the experimental procedure, offer at least two rational explanations for this apparent violation of the law of conservation of mass.

Answer 1

Missy--
This is the first of three posts I've read today by you, all dealing with Cu and/or Cu3(PO4)2. Yet you give no clue as to what experiment you are doing, what has been added, or any of the details. If you want help here you must provide more data than that. I will ignore the other two posts (later than this one).

Answer 2

the experiment is a sequence of Chemical Reactions. Procedure part A preparation fo copper (II) Hydroxide-get a solution of copper(II)nitrate. measure 25ml of solution. to blue solution add 2mL of concertarted NaOH while stirring. Let mixture settle and use litmus paper to test acidity. add addition 10 drop portions of 6M NaOH while stirring until basic. Add 30 mL of water to beaker stir well and allow misture to settle. pour off major part of clear, colorless liquid into a beaker. Save precipitate and residual liquid for part B. Part B-Add dilute (3M) H2SO4 with constant stirring to beaker containing supsension of Cu(OH)2. save color solution of CuSO4 for part C. Part C-add 6M NaOH with constant stirring to colored solution from B until a small amount of blue is visable. Add about 10mL of Na3PO4 solution stirring thoroughly. test with litmus paper. Part D-Add 15mL of 6M HCl to solution from part C. When precipitate is gone filter solution using long stemmed glass funnel and filter paper. Wash filter paper with 20 drops of de-ionized water through filter into beaker containing CuCl2 solution. Part E-to solution CuCl2 add 4 or 5 pieces of magnsium turning and keep them submerged with tip of stirring rod. Add minumum possible quality of concentrated (12M) HCl, to destro excess magnesium. Allow copper to settle. Discard major part of liquid and wash solid copper dust 4 times with 15mL portions of de-ionized water. drain as much water as possible leaving behind copper. place beaker on hot plate and heat until completely dry. after cooled weigh to nearest .001g and record mass. transfer all dried copper onto weighing paper.
Mass of beaker with copper=57.758g
Mass of copper=.243g
.157M X.025L=.003925mols
.003925molsX (1 molCu/i mol Cu(NO3)2) X (63.55g Cu/1 mol Cu)=.25
.243/.25=97.2 % yield