A. Zine Chloride 1. Mass of evaporating dish and zinc 2. Mass of evaporating dis

Question

A. Zine Chloride 1. Mass of evaporating dish and zinc 2. Mass of evaporating dish 3. Mass of zine 4. Mass of evaporating dish and zine chloride first determination 18 262 weeond-determintion third determination 5. Mass of zine chloride 6. Mass of chlorine in zine chloride nc 7. Empirical formula for zine chloride (show calculations) 8. Balanced chemical equation for the formation of zinc chloride from zinc and HCI B. Copper Sulfide 23531 g 1. Mass of crucible, eever, and copper 2. Mass of crucible and cover 3. Mass of copper 4. Mass of crucible, cover, and copper sulfide: first determination 3.1 5. Mass of copper sulfide

Explanation / Answer

B. Copper sulfide

3. mass Cu = 1.555 g

moles Cu = 1.555 g/63.546 g/mol = 0.024 mol

6. mass of sulfide = 1.15 g

moles sulfide = 1.15 g/32.065 g/mol = 0.036 mol

divide by smallest factor

Cu = 0.024/0.024 = 1

S = 0.036/0.024 = 1.5

7. empirical formula = CuS1.5

8. Equation,

Cu + S --> CuS

Post lab

1. Molecular formula of the compound can be found out by percentage of atoms in a compound. The calculation above however, did not result in correct values due to error in measurement of weights during experiment.

2. The ratio (molecular formula weight/empirical formula weight) multiplied by empirical formula would give us the molecular formula of the compound.

3. Yes we can determine the atomic weights of Zn or Cu from the given experiment as in both cases the Zn or Cu is 1 atom per molecule of ZnS or CuCl2.

4. moles Zn = 3.57 g/65.38 g/mol

                    = 0.055 mol

moles of ZnCl2 formed = 0.055 mol

mass of ZnCl2 formed = 0.055 mol x 136.286 g/mol

                                    = 7.50 g

5. Balanced equation,

Al2S3 + 6H2O --> 2Al(OH)3 + 3H2S

moles Al2S3 = 5.50 g/150.16 g/mol = 0.037 mol

moles Al(OH)3 formed = 0.037 mol x 2 = 0.074 mol

mass Al(OH)3 formed = 0.074 mol x 78.0 g/mol = 5.772 g

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