Question

Shown below are the 4 reactions involved in the Cu cycle listed in random order.

a.Cu(PO)(s) + 6HCl(aq) → CuCl(aq) + 2HPO(aq) 


b.CuCl(aq) + Mg(s) → MgCl(aq) + Cu(s) 


c.Cu(s) + 4HNO(aq) → Cu(NO)(aq) + 2NO(g) + 2HO(l) 


d.3Cu(NO)(aq) + 2NaPO(aq) → Cu(PO)(s) + 6NaNO(aq) 


Is the order C, D, A, B?

The first reaction in the cycle is initiated by adding 6 M nitric acid to elemental copper.

1) Calculate the volume of 6 M HNO3 needed to react with 0.636 grams of Cu.

a) Convert grams Cu to moles Cu 


                                    0.636gCu X (1molCu/63.546gCu)= 0.010mol Cu

b) Calculate the moles HNOneeded for the amount of Cu in part (a) using the balanced chemical equation. 


                                    0.010mol Cu X (4 mol HNO3/ 1mol Cu)= 0.040mol HNO3

c) Calculate the volume of 6 M HNOneeded to provide the moles of HNOin part      (b). 


                                    (0.040 mol HNO3/6M)= 0.007 L

2) Calculate the yield in moles of the copper (II) nitrate that you expect to obtain from 0.636 grams of copper. 


I already calculated the moles of Cu present in 0.636 grams of Cu (calculation 1).

0.010mol Cu X (1mol Cu (No3)2/ 1molCu) = 0.010mol (CuNo3)2

I’m not sure how to start the following problems:

It is now time to calculate the amount of the next reagent needed for the 2nd reaction in the cycle involving copper nitrate.

The following reagents are available to carry out the rest of the reactions in the copper cycle.

elemental magnesium


6 M hydrochloric acid

0.5 M sodium phosphate

3) For the second reaction in the cycle, use the moles of copper (II) nitrate expected at the end of the first reaction in the cycle as the starting point for the next calculation.

a) calculate the volume in mL or the mass in grams of the appropriate reagent needed for the next reaction in the cycle. 


b) calculate the yield in moles of the copper product produced by the 2reaction.

2) Repeat the calculation for the next reaction in the cycle until you have calculated the 
amounts of all reagents needed for each reaction in the entire copper cycle. 


Be sure you are explicit in your calculations and include all formulas and units. Be sure that you use the expected yield of copper product from one reaction as the starting amount of copper reactant for the calculation for the next reaction in the cycle.

3) For the final reaction in the cycle,

a) Calculate the yield in grams of solid copper that should be obtained.

Write a formula to express the yield of copper in grams at the end of the copper cycle as a percentage of the mass of Cu started with in the reaction between Cu and HNO3.

Answer 1

Yes, the order is C,D,A,B.

1 mole of Cu(NO₃)₂ is formed from 1 mole of Cu. So, moles of Cu(NO3)2 formed = 0.01 mole

In the second stage of the reaction 0.01 mole Cu(NO3)2 will react with Na3(PO4). The reaction is as follows:

3 Cu(NO3)2 + 2 Na3(PO4) = Cu3(PO4)2 + 6NaNO3

So, three moles of Cu(NO3)2 reacts with 2 moles of Na3(PO4). So, moles of Na3PO4 required = 2 *0.01/3 = 6.67 *10^-3 moles of Na3PO4.

6.67 *10^-3 moles of Na3PO4 =  6.67 *10^-3 mole * 163.94 g/mol = 1.093 gm

2.(a) 1.093 gm Na3PO4 is required for the next reaction.

(b) moles of copper product formed = 0.01/3 = 3.33 *10^-3 moles.

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In the third stage of the reaction Cu3(PO4)2 reacts with HCl. the reaction is as follows.

Cu3(PO4)2 + 6HCl ----> 3CuCl2 + 2H3PO4

1 mole of Cu3(PO4)2 rreacts with 6 moles of HCl.

Moles of Cu3(PO4)2 = 3.33 *10^-3 moles. Moles of HCl = 6 * 3.33 *10^-3 moles = 0.02 moles

The HCl solution is 6M in concentration which means that 6 moles HCl is present in 1000mL solution. So, volume of solution that contain 0.02 moles HCl = 1000mL *0.02moles/6 moles = 3.33 mL

3.33mL 6M Hcl solution will required for the 3rd stage of the reaction.

yield of copper product = 3 * 3.33 *10^-3 = 6.66 *10^-3 moles

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CuCl2 + Mg ----> MgCl2 + Cu (s)

moles of Mg = moles of CuCl2 = 6.66 *10^-3 moles = 0.16 gm

Moles of Cu formed = 6.66 *10^-3 moles =3.81 gm

So, 3.81 gm Cu(s) will be obtained at the end of the reaction.

The formula is = (mass of Cu obtained at the last stage/ mass of Cu used in the first reaction ) *100