Principles of Chemistry II

Laboratory 7 Procedure : The Chemistry of Metals: Exploring Reactivity

Background:

Let’s consider single displacement reaction, where one element displaces another in a compound. This reaction can be summarized by the following general equation:

A(s) + BC(aq) => B(s) + AC(aq)

Figure 1: A is a free metal (s), BC is an ionic compound dissolved in water (aq), B is a free mental (s), and AC an ionic compound dissolved in water (aq).

In this type of reaction, there is a competition between the two elements (A and B). During this single displacement, redox reaction one element loses electron (or electrons) to the other element.
We can simplify the reaction by writing net ionic equation, that will show only the electron exchange between elements:
A(s) + B+ (aq) => A+(aq) + B(s)
Figure 2: A(s) is a free metal that is donating an electron and dissolving into the solution-forming cation A+(aq), a cation B+ (aq) is accepting an electron and converting to the free metal B(s).
Above reaction occurs when free metal A(s) is more reactive then ion B+ (aq) in the solution.
However, in cases where free metal A(s) is less reactive then ion B+ (aq) the reaction does not occur.
There are four signs to look for, when analyzing a chemical reaction:
⦁ Dramatic color change
⦁ Gas evolution (formation of bubbles)
⦁ Precipitate formation (formation of the solid)
⦁ Temperature change

In this lab you will determine order the relative reactivity of four metals: copper, magnesium zinc and led by performing series of redox reactions.

The main objective of this lab is to enhance your understanding of relative reactivity of metals.

Before you start this laboratory assignment, you are encouraged to research relative reactivity series and read pages 651-653 in your Textbook. Throughout this laboratory assignment, you will be required to analyze a chemical reaction in terms of single displacement redox reaction. Be sure to record all observations and any relevant notes that you think you will need to include in your laboratory report.

Take a moment to formulate and write down a hypothesis answering the question what group of metals is more reactive alkaline earth metals or transitional metals?

Pre-Lab questions:

⦁ Using your own words, explain what is a relative reactivity?

⦁ What is a redox reaction?

 

⦁ What happens to the electrons during a redox process?

Procedure:

Preparing the Lab 5

From the course home page, click on the Virtual Lab Tutorial link to watch the overview of using the virtual lab.
⦁ From the course home page, access the lab environment by clicking on the Virtual Lab
link.
⦁ After the lab environment loads, click ‘File’ then ‘Load an Assignment.’
⦁ Select the ‘Redox’ category,
⦁ Select the ‘Redox Reaction Series’ assignment.
⦁ At this point, you have prepared the laboratory for the first experiment with the require supplies to complete your experiments.
⦁ If you haven’t already done so, formulate a hypothesis what group of metals is more reactive alkaline earth metals or transitional metals? as you will need to include this in your final report.

Performing the Experiment

⦁ Select the ‘Solutions’ tab in the stockroom if it is not already selected. Then, select the Erlenmeyer flask containing the ‘0.1M magnesium nitrate solution’ to move it to the workbench.

⦁ Select the ‘Solids’ tab in the stockroom. Then, select the container with ‘Cu’ metal and move it to the workbench.

⦁ From ‘Glassware’ select 250 Erlenmeyer flask, and 5 mL pipette.

⦁ Transfer 5 mL of ‘magnesium nitrate’ to the empty 250 mL Erlenmeyer flask. Record its temperature.

⦁ Transfer 1.0 g of ‘Cu’ to the 250 mL Erlenmeyer’s flask containing magnesium nitrate solution.

 

⦁ Record the temperature, and any other possible changes to the reaction mixture.

⦁ After you record your data, clear the workbench, and start again for the next solution/metal combination listed in the table in the Data Table.

Data Collection Data Table:
Solution Temperature Metal Signs of Reaction Net Ionic Equation
Mg+2 Cu
Zn+2 Cu
Pb+2 Cu
Cu+2 Mg
Zn+2 Mg
Pb+2 Mg
Cu+2 Zn
Mg+2 Zn
Pb+2 Zn
Cu+2 Pb
Mg+2 Pb
Zn+2 Pb

Data Analysis

⦁ Carefully analyze the Data collected in the Data Table.
⦁ Arrange the four metals in order of their increasing relative reactivity. From least reactive to the most reactive.
⦁ Write details justification for your selection of the order.
Notes
This section should include notes about any observations or data collected during the lab.

Report Requirements
This section contains key information that must be included in your typed report.

⦁ Define the problem in a manner that is clear and insightful.
⦁ Identify the strategies and procedures used during the lab.
⦁ Clear hypothesis statement and other potential solutions that identify any relevant contextual factors (i.e. real-world costs).
⦁ Clear presentation of data including any tables or other figures that are relevant to understanding your stated conclusions at the end of the report. Include any relevant calculations performed during the lab.
⦁ Clearly stated results and discussion of possible improvements to the procedure.
⦁ Conclusive statements arguing in favor of your findings.

Note: All reports will be graded using the rubric embedded within the course.