Reactivity of Metals Laboratory for electrochemistry Purpose To measure the relative reactivities of selected metallic elements.

Background Elements have different uses depending on their reactivity. Gold is commonly used in jewelry because it is so resistant to chemical reactions. Sodium is not used in jewelry because it explodes when it contacts water. Differences in chemical reactivity depends on the relative ease with which elements give up electrons.

Background, cont. You can measure relative reactivity of two metals by placing a sample of one metal in a solution of the ions of the other metal. If the solid metal sample is more reactive, electrons will move from the metal into the solution and the solid sample will become ions and dissolve. Meanwhile, the less reactive ion sample will take the electrons and form a solid.

Background, cont. This is an example of a redox reaction because electrons are transferred from one species to another. If the solid sample is less reactive than the ionized metal solution, no reaction will occur.

Your Mission To test the reactivities of a variety of metals with different metal ions. To write chemical equations for each reaction that occurs. To then use the results of your tests to construct a scale of relative reactivities of the metals..

Materials needed per group Goggles and aprons; gloves are recommended Labels or grease pencil or sharpie marker Well plate Forceps Steel wool or sand paper (to polish any corroded solid metal samples) Chemicals supplied Copper wire or mesh Lead strips Magnesium ribbon 2.5% lead (II) nitrate solution 2.5% copper (II) nitrate solution 2.5% magnesium nitrate solution

Procedure Labs need to be written in the 2 nd person, singular, present tense, neutral gender. “add 5 drops of copper nitrate solution” Instead of “we added the magnesium to the test tube” write “add magnesium to the test tube” Caution! Be familiar with the hazards associated with chemicals before handling them! Read bottles, refer to MSDS information, ask questions.

Procedure, cont. These are the metals you will be testing: Lead, copper, magnesium Write a procedure to combine each solid metal with a solution that does not contain the metal ion that is being added (ASK), using the chemicals that are provided, so that you will have the data you need to put the metals in order of increasing reactivity. Plan this before you begin working in the lab.

Data and Observations Construct a table to record data and observations. Here is a suggestion: WellMetal ion MetalObservations 1Pb 2+ Cu

Calculations Write unbalanced half equations and determine the flow of electrons and the voltage for the reactions in the wells. label what is oxidized and what is reduced. Write the full reaction. State if reaction is spontaneous or non-spontaneous Ex. F è  2F - = 2.87 volts Reduced Pb  Pb è = 0.13 volts Oxidized 3.00 volts = spontaneous Full reaction F 2 + Pb  Pb +2 + F -

Conclusions State the reactivities of the metals from the least to the most reactive. Each metal should have two pieces of evidence as to its’ reactivity compared to the other metals. These should be statements that compare the reactivities of each of the elements citing laboratory data as evidence to support each conclusion. –Ex. Sodium is more reactive than Magnesium. When solid sodium and magnesium ion were combined a reaction occurred, as indicated by bubbling and heat. When solid Mg was introduced into the sodium ion solution there was no reaction.

Discussion Specifically discuss –What redox reactions are –How you know which metal is oxidized and which is reduced (make sure to mention electronegativity) –How you determine which metal is more reactive –How you can determine whether reactants or products are favored

There are no sources of error with this lab The calculation section will count twice on the lab report