Silver from a copper strip
A copper strip in silver nitrate solution grows grey crystals of silver while the solution turns blue with copper ions. The equation takes one copper for TWO silvers, and silver atoms are heavier than copper ones. This activity has you work out both masses: the copper that dissolved and the silver that formed.
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5 steps · Mole Concept · Stoichiometry · Metals and Non-metals
What you will use
Apparatus
- Beaker
Chemicals
- Silver Nitrate Solution
- Copper Strip
The steps
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Pour silver nitrate solution into the beaker, and choose 0.5 M.
Colourless, and five millimoles of silver ions.
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Put a copper strip in.
Grey silver grows on the strip, and the solution turns faintly blue.
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Which reagent ran out? Give its formula.
Divide by the equation's numbers first: silver nitrate is needed two at a time.
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How many grams of silver formed?
One Ag for every AgNO₃, at 107.9 g/mol.
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How many grams of copper are left of the 1 g strip?
Half as many moles of copper reacted as of silver formed. Compare the two masses: more silver was made than copper was used.
What it shows
Mass is not what an equation balances. It balances atoms, and the moles follow the atoms. One copper frees two silvers, and two silvers weigh more than three times as much as the copper they replaced.