Zinc Chloride Lab Report

8. Balanced chemical equation for the formation of zinc chloride from zinc and HCl First, we set up the equation xZn(s) + yHCl(aq) → ZnxCly (s) + y/2H2(g) . We knew the empirical formula for zinc chloride is ZnCl8. Based on the law of conservation of matter, we got the balanced equation:

Balanced equation: Zn(s) + 8 HCl(aq) → ZnCl8 (s) + 4 H2 (g)

9. Percentage Error Calculation: Experimental values: (1.8+4.34)/2= 3.07g (average mass) Accepted values: 2.67g ZnCl8 0.5g Zn x 1mol Zn/65.4g Zn x 1/1 x 349.4g ZnCl8/ 1 ZnCl8 mol = 2.67g ZnCl8 l 3.07g-2.67gl / 2.67 x 100 = 14 %

B Copper Sulfide

Trial 1 Trial 2 Trial 3

1.Mass of crucible, cover and copper 22.82g 21.04g 22.87g

2.Mass of crucible and cover 20.91g 20.61g 21.49g

3.Mass of

And the mixture turned black after heated it with strong flame for 5 minutes. The mass of copper was found by subtracting the mass of crucible and cover from the mass of the crucible, cover, and copper. Also, the mass of copper sulfide was calculated by subtracting the mass of crucible and cover from the mass of crucible, cover, and copper sulfide. Then the mass of copper sulfide was subtracted by the copper to get the mass of sulfur.

7. Empirical Formula for copper sulfide:Cu2S

In order to determine the empirical formulas, the mass in grams is converted to moles.

Average mass of copper: 1.24g Cu

Average mass of sulfur: 0.28g S

1.24g Cu X 1 mol Cu/ 63.55g Cu = 0.0195mol Cu

0.28g S X 1 mol S/ 32.07g S = 0.0087mol S

Then, to find the smallest whole number ratio, we divided each number of moles by the smallest number. The ratio is 2Cu:1S, so the empirical formula is Cu2S

0.0195mol Cu / 0.0087mol S= 2

0.0087mol S / 0.0087mol S = 1 8. Balanced chemical equation for the formation of copper sulfide from copper and sulfur.

First, we set up the equation xCu(s) + yS(s)→ CuxSy (s) . We knew the empirical formula for copper sulfide is Cu2S. Based on the law of conservation of matter, we got the balanced equation:

2Cu + S = Cu2S

9.Percentage Error

Can you determine the molecular formula of a substance from its percent composition? A: Yes.

2. Given that zinc chloride has a formula weight of 136.28 amu, what is its formula? A: ZnCl2

3. Can you determine the atomic weights of zinc or copper by the methods used in this experiment? How? What additional information is necessary in order to do this? A: Yes, we need molar mass of sulfur, hydrogen, and chlorine. Then set the molar mass of copper and zinc to x and y. And use the mole ratio, which is 1:1 for two reactions to solve the unknown.

4. How many grams of zinc chloride could be formed from the reaction of 3.57g of zinc with excess HCl? A: 3.75g x 1mol/ 65.39g x 1 mol/ 1mol x 136.4g / 1 mol = 7.45g.

5. Aluminum sulfide reacts with water to form aluminum hydroxide and hydrogen sulfide. (a) Write a balanced equation for this reaction. (b) How many grams of aluminum hydroxide can be obtained from 10.5g of aluminum sulfide? A: (a): Al2S3 + 6 H2O → 2 Al (OH)3 +