Questions 22-24 refer to the following information. A group of students was asked to recover Cu(s) f — Stoichiometry Chemistry Question
Question
Questions 22-24 refer to the following information.
A group of students was asked to recover Cu(s) from a blue-green aqueous solution containing an unknown concentration of Cu2+(aq). The students took a 100.0 mL sample of the solution and added an excess of 1.0 M Na3PO4(aq), causing the Cu2+(aq) to precipitate as Cu3(PO4)2(s), as shown in step 1 below.
Step 1: [VISUAL]
The Cu3(PO4)2(s) was filtered, dried, and weighed. Then the Cu3(PO4)2(s) was dissolved in a 3.0 M HCl(aq) solution, as shown in step 2 below.
Step 2: [VISUAL]
The students added a strip of Zn(s) to the solution to recover the Cu(s) as shown in step 3 below.
Step 3: [VISUAL]
Finally, the Cu(s) was filtered, dried, and weighed.
- The mass of the Cu(s) produced in step 3 was slightly more than the mass predicted from the 3.8 g of Cu3(PO4)2(s) recovered from step 1. Which of the following could account for the discrepancy in the yield of Cu(s) from step 3 ?
All of the Cu3(PO4)2(s) dissolved in the HCl(aq) .
Some of the Cu(s) adhered to the side of the funnel used to filter the solution.
Some unreacted Zn(s) was mixed in with the Cu(s) .
Too much Na3PO4(aq) was added to the original Cu2+(aq) solution.