Lab #7 Mass and Moles: Silver Nitrate and Copper
Lab #7 Mass and Moles: Silver Nitrate and Copper
Purpose:
To investigate mass/mole relationships in chemical reactions
To further develop an understanding of oxidation/reduction reactions
Background:
Chemical equations are balanced to show conservations of atoms or matter. The balanced chemical equation shows the ratio of particles in combinations. The coefficient shows the number of particles and also the number of moles. Since the particles are too small to be counted, moles are considered instead. A mole is 6.022 x 1023 particles. Since we can only measure the mass, the mole allows us to compare the number of particles by using the molar mass to calculate the number of moles.
Pre-Lab Questions:
1. Write a balanced equation the reaction of aluminum with hydrochloric acid (single replacement reaction).
2. Based on the balanced chemical equation,
how many moles of hydrochloric acid are required to form one mole of hydrogen gas?
a. If 10.0 moles of aluminum react, how many moles of hydrogen gas can be expected?
b. If 25.0 g. of aluminum chloride are produced, how many moles of aluminum reacted?
3. Describe the reaction in detail.
a. What happens to the aluminum? Was it oxidized or reduced? Write the half-reaction.
Describe the bonding (or attractions) and arrangement of the particles before and after.
Draw the electron configuration of aluminum before and after the reaction.
Explain when it is more stable
b. What happens to the hydrogen ions? What happens to the bonds? Was it oxidized or reduced? Write the half-reaction.
c. What happens to the chloride ions?
d. Write a net ionic equation for the reaction.
e. Both silver and copper do not react with hydrochloric acid. Explain why.
Procedures:
Copper will be reacted with silver nitrate in a single replacement reaction. The mass of the copper will be measured before and after reacting. The solid product will be isolated and measured.
Read the procedures. Construct two tables- one for qualitative data- observations and another for quantitative data- measurements. All the data that needs to be recorded is underlined.
A. Measure the mass of copper to be reacted. Prepare the wire to be reacted by coiling it around a pencil to form a neat coil. Use a piece of wire with a mass greater than .25 grams.
B. Label an empty 100 - 150 mL beaker with a grease pencil or permanent marker. Measure and record the mass of the empty 100 or 150 mL beaker.
C. Add between 20.0 - 25.0 mL of 0.15 M silver nitrate solution. Measure and record the exact volume of 0.15 M silver nitrate solution added.
D. Record observations of both reactants.
E. Place the copper wire in the silver nitrate solution. Monitor the reaction until you can make two observations about the reaction: one about a change in the solid copper and another about the change in the solution. Record both observations of the reaction.
F. Allow the reaction to go to completion overnight. Recordobservations the next day.
G. Use tweezers to remove the remaining copper wire from the solution. Rinse off any remaining silver particles over the beaker before removing the wire. Scrape off any excess particles, if necessary.
H. Set the copper wire aside to allow it to dry. Once dry, measure and record the mass of the remaining copper wire.
I. Decant the liquid and solid remaining in the beaker in order to isolate the silver. Carefully pour off the liquid into another beaker. Directing the flow of liquid down a stirring rod.
J. After decanting, rinse the solid with 25 mL of water and decant again. Repeat rinsing and decanting, until the solution is colorless.
K. Dry the remaining silver to isolate the silver solid.
L. Once dry, measure and record the mass of silver produced in the beaker.
M. Write a description of the procedures in the lab. Include the following in your description. Why was the solution decanted? Why was the remaining product dried in the oven?
Preliminary Mass Analysis:
Calculate the moles of silver that will be produced if all the copper reacts.
Calculate the moles of silver that will be produced if all the silver nitrate reacts.
Based upon these calculations, which reactant do you expect to be used up first. Explain.
This is the limiting reactant. This quantity limits the amount of product that can be produced.
Analysis of the Reaction:
4. Copper particles are changed in the reaction. Describe the copper before the reaction. Include number protons and electrons. Draw the electron configuration. Is it an atom or ion?
5. What happens to the copper in the reaction? Was it oxidized or reduced? Write a reaction to summarize the change (a half-reaction)- include the electrons. What ions of copper may be formed in the reaction of silver nitrate and copper? How are these ions formed?
6. Write two balanced equations to show the formation of both possible copper ions. Label which ion is produced for each reaction.
7. If the copper (II) ion is formed, what is the mole ratio of copper consumed to silver produced?
If the copper (I) ion is formed, what is the mole ratio of copper consumed to silver produced?
8. Silver particles are changed in the reaction. Describe the silver before the reaction. Include the number of protons and electrons? Is it an atom or an ion? Draw the electron configuration.
9. What happened to the silver ion in the reaction? Write a reaction to summarize the change (a half-reaction)- include the electrons.
10. What kind of reaction is this? How does the activity of copper and silver compare?
11. Changes in Appearance.
a. What color is the silver ion in solution? What color is the silver atom in the solid?
b. What color is the copper atom in the solid? What color is the copper ion in solution?
c. Explain the color change in the solution as the reaction progresses.
Calculations:
12. Determining which ion of copper was formed:
a. Calculate the moles of copper consumed. Show your complete calculation.
b. Calculate the moles of silver actually produced. Show your complete calculation.
c. Write the molar ratio of copper consumed to silver produced. Which ion of copper was produced based upon your data? Justify your answer with lab evidence and the balanced equation.
13. Determining percent yield.
a. Calculate the number of moles of Ag expected based upon the moles of Cu actually consumed.
b. Calculate the percent yield.
14. Describe how to prepare 50.0 mL of 0.20 M AgNO3 from the solid.
15. Describe how to prepare 50.0 mL 0.20 M AgNO3 from a stock solution of 0.500 M solution.
Additional Questions (HP)
16. Write the balanced equation for the reaction forming copper (II) ion in solution and show the oxidation numbers of each element in the reaction.
17. Calculate the percent by mass of silver in silver nitrate.
18. If sodium hydroxide solution is added to the remaining solution, a blue precipitate forms.
a. Write a balanced equation for the reaction of the copper(II) nitrate in solution with NaOH(aq).
b. What is the blue precipitate. What do you know about the Ksp of this precipitate?
c. The Ksp of copper (II) hydroxide is 2.2 x 10-20. Calculate the molarity of the copper (II) hydroxide that remains in solution when the precipitate forms.
19. If 2.00 grams copper(II) nitrate is formed in 50.0 grams of water, calculate
a. molality of the solution
b. percent by mass of the solution
c. the mole fraction of copper(II) nitrate in the solution
d. explain why you cannot calculate the molarity
20. Draw the Lewis structure for the nitrate ion. Determine the formal charge on each atom.
Describe the resonance structures and formal charge.
Identify the both the electron pair and molecular geometry of the nitrate ion.
Determine the hybrid orbitals of the nitrogen atom in the nitrate ion.
Lab #7 worksheet #1Name ______period____
Aluminum reacts with copper (II) chloride in a single replacement reaction.
experimental data
mass of aluminum before 5.00 grams
mass of copper (II) chloride added to produced 200.0 mL of solution 20.00 grams
mass of aluminum remaining 2.97 grams
mass of copper produced 6.88 grams
1. Write the balanced equation for the reaction.
2. Calculate the mass of copper expected based on aluminum consumed.
3. Calculate the percent yield.
4. Calculate the mass of copper (II) chloride required to completely react with all of the aluminum.
5. Calculate the mass of copper that would be produced if all the copper (II) chloride in the solution reacts.
6. Calculate the mass of copper that would be produced if all the aluminum reacted.
7. Use your calculations from 5 and 6 to explain which reactant is the limiting reactant. (Will be used up first- limits the amount of product that can be produced)
a. What reactant will remain when the reaction stops? Explain how you know.
b. What will you need to add to get the reaction to continue? Explain how you know.
11. Calculation of Concentration
a. Calculate the molarity of the copper (II) chloride solution that was prepared.
b. Calculate the molality if 195.6 grams of water was added to prepare the solution.
c. Calculate the percent by mass
12. What happened to the aluminum? What kind of particles at the beginning and end? What kind of bonds? Draw the electron configurations before and after. Write a half-reaction to show the change. Was it oxidized or reduced?
13. What happened to the copper? What kind of particles at the beginning and end? What kind of bonds? Draw the electron configurations after. Write a half-reaction to show the change. Was it oxidized or reduced?
14. What happened to the chlorine? What kind of particles at the beginning and end? What kind of bonds? Draw the electron configurations before and after. Write a half-reaction to show the change.
15. Which is more active copper or aluminum? Explain how you know.
Stoichiometry Worksheet #1name______period____
formulas, balanced equations and masses
For each reaction
1.Write the formula for the products and reactants
2.Balance the equation
3.Identify starting point and endpoint
4.Select and show factors to get you get you to the end
Sodium reacts with water to produce a metallic hydroxide and hydrogen gas.
balanced equation (mole ratio- particle numbers)
Calculation of expected mass
10.0 grams of sodium will produce how many grams of sodium hydroxide?
Iron (III) oxide reacts with carbon monoxide to produce iron and carbon dioxide.
balanced equation (mole ratio- particle numbers)
Calculation of expected mass
22.0 grams of iron (III) oxide can be reacted to recover how many grams of iron?
Calcium hydroxide and phosphoric acid react to form calcium phosphate and water.
balanced equation (mole ratio- particle numbers)
To form 25 grams of calcium phosphate, how much grams of calcium hydroxide will be required?
How many mL of 0.50 M phosphoric acid will be required?
Chlorine gas is bubbled through an aqueous solution of magnesium bromide to yield an aqueous solution of magnesium chloride and bromine gas.
balanced equation (mole ratio- particle numbers)
Calculation of expected mass
How many grams of magnesium bromide will completely react with 130.0 mL of chlorine gas at STP?
Remember one mole of a gas at STP has a volume of 22.4 L.
Stoichiometry Worksheet #2name ______period____
1.How many grams of calcium oxide reacts with excess hydrochloric acid to produce 100.0 grams of calcium chloride (and water also produced). (single replacement)
2.If 20.0 grams of zinc react with excess hydrochloric acid, how many liters of hydrogen gas will be produced at STP? (single replacement- zinc chloride also produced) Remember one mole at STP is 22.4 L
3.How many moles of chlorine gas must be reacted with excess sodium iodide to produce 10.0 grams of sodium chloride? (single replacement- NM replaces Nm))
4.How many moles of oxygen are produced in the decomposition of 5.00 grams of potassium chlorate? (potassium chloride is also produced)
5. How many grams of copper are required to react with 4.00 grams of silver nitrate, which is dissolved in water? (Single replacement with copper (II) ion formed)
6.If excess ammonium sulfate reacts with 20.0 grams of calcium hydroxide, how many grams of ammonia are produced? (other products are calcium sulfate and water)
7.If excess sulfuric acid reacts with 30.0 grams of sodium chloride, how many grams of hydrogen chloride and sodium sulfate are produced?
Stoichiometry Worksheet #3Name ______period____
1. If 32.0 grams of aluminum react with excess hydrochloric acid, how many grams of aluminum chloride will be produced? (single replacement reaction)
2. How many grams of sodium hydroxide are needed to completely neutralize 25.0 grams of sulfuric acid?
3. Molten iron and carbon monoxide are produced in a blast furnace by the reaction of iron (III) oxide and carbon. If 25.0 grams of pure iron (III) oxide are used, how many moles of iron are produced?
4. Iron (II) sulfide reacts with hydrochloric acid to produce iron (II) chloride and hydrogen sulfide gas. How many grams of iron chloride will be produced if 2.46 grams of iron (II) sulfide are consumed?
5. If a plant is required to make 30.0 grams of glucose, C6H12O6 through the process of photosynthesis from carbon dioxide and water, how many grams of water are required? Remember that oxygen is also produced in this reaction.
6. Chlorine gas reacts with sodium bromide in an aqueous solution. (single replacement) How many grams of sodium chloride will be produced if .37 moles of chlorine are reacted?
7. How much silver phosphate is produced if 10.0 grams of silver acetate are reacted with excess sodium phosphate?
Stoichiometry Worksheet #4name ______period_____
1. How much nitrogen is required to produce 75.00 kg. of ammonia gas when it is reacted with excess hydrogen?
2. When 12.5 grams of C8H18 are burnt with excess oxygen, how much water is produced?
3. If 5.00 grams of carbon dioxide are collected from the combustion of glucose, how many grams of oxygen are comsumed?
4. 25.00 grams of mercury was produced in the decomposition of mercuric oxide. How much oxygen was produced?
5. Hydrogen and oxygen gas react to form water when an ignition source is available. How much hydrogen and oxygen gas are required to produce 18.5 grams of water?
6. 4.50 grams of chlorine gas are added to excess magnesium bromide to produce how many grams of bromine?
7. How much silver phosphate is produced if 10.0 grams of aqueous silver acetate reacts with excess aqueous sodium phosphate in a double replacement reaction?
8. How much zinc will react with 24.5 mL of 2.00 M HCl?