1) can you determine the molecular formula if a substance from its percent compo

Question

1) can you determine the molecular formula if a substance from its percent composition.

2) given that zinc chloride has a formula weight of 136.28amu. what is its formula?

3) Can you determine the atomic weights of zinc or copper by the methods used in this experiment? if so how? what additional information is necessary to do this?

4) How many grams of zinc chloride could be formed from the reaction of 3.57g of zinc with excess HCI?

5) Aluminum sulfide reacts with water to form aluminum hydroxide and hydrogen sulfide. a) wrote a balance equation for this reaction. B) how many grams of aluminum hydroxide can be obtained from10.5g of aluminum sulfide.

6) when coppper(I) sulfide is partially roasted in air ( reaction with O2) sulfite is formed first. subssequently, upon heating , thr copper sulfite thermally decomposes to copper(I) oxide and sulfur dioxide. write balanced chemical equation for these two reactions.

Explanation / Answer

1) the percent composition may only give you an empirical formula. To get the molecular formula, you also need the molecular weight.

2) Zinc = 65.38

Chlorine = 35.453

Only suitable combination is ZnCl2

3) *Experiment not included*

4) Zn + 2HCl -> ZnCl2 + H2

3.57 g of zinc (1 mol/65.38 g) = 0.0546 moles

0.0546 moles of ZnCl2 (136.28 g / mol) = 7.44 grams

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

b) 10.5 g of Al2S3 (1mol /150.158g) = 0.06992 moles of Al2S3 (2 moles Al(OH)3/1 mol of Al2S3) =

0.1399 mol of Al(OH)3 (78 grams / mol) = 10.91 grams of Al(OH)3

6) Cu2S + 3/2 O2 -> Cu2SO3

Cu2SO3 -> Cu2O + SO2

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