A
SILVER AND COPPER REACTION
Purpose
The purpose
of this investigation is to show how molecular weight can be used to show that
elements combine in whole number ratios.
Introduction
Zinc metal will react with an acid to form
zinc ions and hydrogen gas. A solid
metal may dissolve in the presence of other materials, as well. For example, silver ions react with copper
atoms. The silver ion takes the copper’s
electrons, to become solid silver, while the solid copper atom becomes an aqueous
copper ion:
____ silver
ion(s) +
____ copper atom(s) –> ____
silver atoms + ____ copper ions
The goal of
this activity is to discover how many silver ions react with how many
copper atoms. That is the reason for the
blank lines in the equation. Of course,
the number of silver atoms on one side of the equation must equal the number of
silver ions on the other side of the equation, and the same is true of the
copper atoms and ions.
Instructions
Weigh a piece
of copper wire. Put the wire into a test
tube containing an aqueous solution of silver nitrate. Allow the reaction to proceed for at least
thirty minutes.
Remove the
copper wire from the test tube, and scrape off the silver. Dry the copper with
paper towels and weigh it again. The
difference in mass is the amount of copper reacted.
Collect all
the solid silver formed. Wash it and dry
it in an evaporating dish on a hot plate.
Weigh the silver metal formed.
Divide the
mass of copper reacted by its atomic mass, 63.5 g/mol, to find the moles of
copper reacted. Divide the mass of
silver by its atomic mass, 108 g/mol, to find the moles of silver reacted. Find the simplest whole number ratio to
determine the ‘stoichiometry’ of the reaction.
Results
1.
Initial
mass of copper:
2.
Final
mass of copper:
3.
Mass
of copper reacted (Step 2 – Step 1):
4.
Moles
of copper reacted (Moles = mass/atomic mass):
5.
Mass
of silver reacted:
6.
Moles
of silver reacted (Moles = mass/atomic mass):
7.
Simplest
whole number ratio of silver to copper (Moles Silver / Moles of copper):
Discussion
Questions
1) What evidence do you have that a reaction has
occurred?
2) What aspects of this reaction make it useful
for this type of investigation?