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Chemical Reactions : Types and Equations

Procedure 1
Synthesis:

1. Take a crucible from the Glassware shelf and place it on the workbench.

2. Take a balance from the Tools shelf and drop it on the empty crucible. Record its mass.

3. Add 2g of Mg to the crucible and record its mass.

4. Remove the crucible from the balance.

5. Take a Bunsen burner from the Tools shelf and place it on the workbench. Open the Properties window and click on the Bunsen burner. In the Properties window turn on the burner and select the low flame.

6. Drag the Bunsen burner and drop it on the crucible.

7. Open the Data window and click on the crucible. The Data window displays the contents of the crucible. When the contents change from Mg to "Unknown", remove the crucible from the flame.

8. Measure and record the mass of the crucible and its contents.

Procedure 2

Decomposition:

1. Clear the workbench by dragging all of the Tools and Glassware to the recycle chute.

2. Take a clean 150 mL Erlenmeyer flask from the Glassware shelf and place it on the workbench.

3. Add 5g of copper(II) carbonate hydroxide hydrate, Cu₂CO₃(OH)₂*H₂O.

4. Take a balance from the Tools shelf and drop it directly onto the flask. Record the total mass of the flask and its contents.

5. Remove the flask from the balance.

6. Take a Bunsen burner from the Tools shelf and drop it onto the flask. Use the Properties window to turn the Bunsen burner on and set the flame to low.

7. Watch the flask until the green compound turns black.

8. Remove the flask from the Bunsen burner.

9. Drag the balance and drop it onto the flask. Record the mass of the flask and its contents.

Procedure 3

Single Displacement:

1. Clear the workbench by dragging all of the Tools and Glassware to the recycle chute.

2. Take a clean 150 mL Erlenmeyer flask from the Glassware shelf and place it on the workbench.

3. Add 0.25g of zinc to the flask.

4. Open the Properties window, click on the flask, and back in the Properties window click on the Open/Close icon. This closes the top of the flask with an airtight stopper.

5. Take a thermometer from the Tools shelf and connect it to the flask.

6. Take a pressure gauge from the Tools shelf and connect it to the flask.

7. Add 15 mL of 6M HCl by dragging the HCl solution from the Chemicals shelf and dropping it on the closed flask. The HCl solution is added as if by a syringe poked through the stopper.

8. Observe and record any indication that a reaction has occurred.

9. Wait for the solution in the flask to cool down to at least half a degree within the room temperature of 21C.

10. Remove the thermometer and pressure gauge from the flask.

11. Take gas piston from the Glassware shelf and place it on the workbench.

12. Drag the closed flask and drop it onto the gas piston. This will connect the two and allow gas to escape from the flask into gas piston.

13. Open the Data window and click on the gas piston. Record the volume of the gas collected in the gas piston.

Procedure 4

Double Displacement:

1. Clear the workbench by dragging all of the Glassware to the recycle chute.

2. Take two 50 mL beakers from the Glassware shelf and place them on the workbench.

3. Add 15 mL of sodium hydroxide solution, NaOH to one of the beakers.

4. Add 6 mL of nickel(II) chloride solution, NiCl₂, to the second beaker.

5. Observe the two solutions, and then pour the entire contents of one beaker into another.

6. Record your observations after the reaction occurs.

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Assignment 1 of Procedure 1

1. Record the following:

(a) mass of empty crucible (g):
( my answer 53.2 g )
(b) mass of Mg (g):
( my answer 2g)

(c) mass of the "unknown" product after heating (g):
(my answe 3.316g)
(d) change in mass (g):
(my answer 1.31 g )
2. Where did the extra mass come from? (Hint: what element could have the combined with the Mg?)

3. Write a balanced equation for the synthesis reaction that occurred.

Assignment 1 of Procedure 2

1. A hydrate is a chemical compound that has water molecules bound loosely to it by electrostatic forces. When the hydrated compound is heated, the water molecules are released as water vapor. The formula of the copper carbonate hydrate, Cu₂CO₃(OH)₂*H₂O, tells us that one water molecule is bound to each copper carbonate hydroxide molecule.

From the ratio of the mass of the black product to the initial 5g placed in the flask, could the remaining black compound be the anhydrous copper carbonate hydroxide molecule Cu₂CO₃(OH)₂? The molecular weight of Cu₂CO₃(OH)₂ is 221.116 g/mol, while that of water is 18.015 g/mol. Show your calculations.

2. If the product is NOT anhydrous copper carbonate hydroxide, perhaps the black color provides a hint as to its identity. Identify the product from the following list of copper compounds:

CuCO₃ - light green powder
Cu(OH)₂ - blue green powder
Cu₂O - reddish brown crystals
CuO - black powder

3. Write a balanced equation for the decomposition of copper carbonate hydroxide hydrate.

Assignment 1 of Procedure 3

1. In addition to the gas produced, an aqueous solution of zinc chloride is also produced. Write the formula for this compound.

2. Write a balanced chemical equation for this single displacement reaction. Identify which chemical is replaced and which replaces it.

3. If you could open the piston slightly and place a burning splint into it, you would hear a "pop". What gas would do this? Does this make sense according to the balanced equation for the reaction?

Assignment 1 of Procedure 4

1. What ions are present in an aqueous solution of NaOH?

2. What ions are present in an aqueous solution of NiCl₂?

3. Write a complete, balanced equation for this double displacement reaction. (Hint: the solid is a compound of Ni ions and hydroxide ions.) Don't write the net ionic equation but rather the complete form with neutrally charged compounds with all of the atoms.

Solution Summary

This solution provides an explanation of how to determine balanced equations for chemical reactions.

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