Question

Lab observations :

Exp 1

Empty mass of crucible 88.00

Added 5g of copper sulfate hydrate to crucible

Total mass of crucible and copper sulfate hydrate 93.000

A blue solid is present prior to heating

White steam of water molecules under heat turned to a clear / white appearance powered like

Mass of crucible and reaction of heat copper sulfate hydrate = 91.196

Exp 2

Empty mass of crucible 88.00

Added 5g of Magnesium Chloride hydrate to crucible

Total mass of crucible and Magnesium Chloride hydrate 93.000

A gray/ white solid is present prior to heating heated under bunsen burner

White vapor is produced

No change in color/ appearance

Mass of crucible and left over contents after heating 90.342

1) How many grams of mass were lost during the heating process? Choose the closest answer.

2)How many moles of water were lost during the heating? The molar mass of water is 18.015 g/mol. Choose the closest answer.

3)How many grams of anhydrous copper (II) sulfate were in the crucible after heating? Choose the closest answer

4)How many moles of anhydrous copper (II) sulfate remained in the crucible after heating? The molar mass of anhydrous copper (II) sulfate is 159.609 g/mol. Choose the closest answer.

5)Which of the following represents the balanced chemical equation for this reaction?

Exp 2

1)How many grams of anhydrous magnesium chloride were in the crucible after heating? Choose the closest answer.

2)How many grams of water were lost during the heating process? Choose the closest answer.

3)How many moles of water were lost during the heating? The molar mass of water is 18.015 g/mol. Choose the closest answer.

4)How many moles of anhydrous magnesium chloride remained in the crucible after heating? The molar mass of anhydrous magnesium chloride is 95.211 g/mol. Choose the closest answer.

5)In Experiment 2, which of the following represents the balanced chemical equation for this reaction?

6)Why was mass lost from the crucible during the reaction?

7)Calcium sulfate is a white solid found as two hydrates, a hemihydrate known as plaster of Paris and a dehydrate known as gypsum. The hemihydrate is a white solid as shown in the figure below. Given that the molar mass of the anhydrous calcium sulfate is 136.14 g/mol, the molar mass of the hemihydrate is 145.15 g/mol, and the molar mass of water is 18.015 g/mol, what is the empirical formula of the hemihydrate?

Answer 1

1. Mass of cruicible and copper sulfur hydrate before heating=93 g

mass of crucible and  reaction of heat copper sulfate hydrate-91.196 g

mass lost=93-91.196=1.8 g

2.during heating,only water molecules are lost

moles of water lost=1.8/18=0.1 moles(moles=mas of water lost/molar mass of water)

3.mass of anhydrous copper (II) sulfate left after heating=(mass of crucible +contents ater heating)-mass of cruicible=91.196-88=3.196 g

4.moles of  reaction of heat copper sulfate hydrate left after heating=3.196/159.606=0.02 moles

5. reaction represnting experiment 1 in presence of heat is

CuSO₄.5H₂O-->CuSO₄+5H₂O