Question

Given the following experimentally determined values, answer the questions.

.009070 mol Cl

.00565 mol Cu

.00385 mol Zn

Ratio of Chloride to copper = 1.61:1

Ratio of chloride to zinc = 2.36:1

Ratio of zinc to copper = .681:1

What are your experimentally-determined formulas for (i) copper chloride, and (ii) zinc chloride? Once you have calculated the moles of each element/ion (Cu, Zn, and Cl– ), you can then determine the empirical formula of copper chloride by computing the ratio of the moles of chloride to the moles of copper.  Ionic compounds can only have an empirical formula, meaning that the whole number ratio determined experimentally is the empirical formula. Therefore, the rounding range does not apply for ionic compounds. Once the formulas for copper chloride and zinc chloride have been determined (at this point w, x, y, and z have been determined), you are ready to balance the chemical reaction.

What is the expected formula for (i) copper chloride, and (ii) zinc chloride?

Write the balanced chemical equation for the reaction you carried out, including phases. Use the expected formulas. [a Zn(s) + b CuwClx(aq) → c Cu(s) + d ZnyClz(aq)] You will accomplish this by determining the number of moles of copper, zinc, and chloride ion consumed or generated in the reaction. Once you have determined these quantities you will be able to calculate mole ratios of Cu:Cl (w:x), Zn:Cl (y:z), and Zn:Cu (a:b:c:d), and also write a balanced chemical equation for the reaction you carried out.

From the initial masses of zinc and copper(II) chloride dihydrate (think carefully about that formula), which is the limiting reactant? (Circle it in the line above.) Show how you reached that conclusion.

5.Determine the theoretical yield of copper. How does that compare to the actual amount of copper collected? What was your percent yield of copper?

6.List the two most likely sources of error in this experiment. Which would lead to an erroneously high mass? Which to an erroneously low mass? (gravity and vacuum filtration were used)

7.You washed solid samples with DI-water several times during the experiment. What is the purpose of these washing steps?

Answer 1

Cl: Cu = 1.61 : 1 2:1 ( mole ratio)

Cl: Zn = 2.36: 1 2:1 ( mole ratio)

mole ratio = atom number ratio ( 1 mole hasavogadro number of atoms)

(i) formula of cupper chloride : CuCl₂

(ii) Zinc chloride: ZnCl₂

balanced chemical reaction....

w:x = 1:2; y:z = 1:2 and a:b:c:d = 1:1:1:1

Zn(s) will be the limiting reagent. As, the mole of Zn(s) is lower than mole of cupper chloride thogh stoichiometric coefficient is same for both two reagents. Therefore, lower value of mole number predict the limiting reagent.

from balanced chemical reactions 1mole Zn ( as limiting reagent) produces 1mole Cu (s). so, 0.00385 mole of Zn produces 0.00385 mole Cu. theoretical yield of Cu is 0.00385

% yield = (0.00385 / 0.00565) *100 = 68.14%