Brass Penny Lab
In this lab you will be coating a
copper penny with zinc metal and then heating the coated penny to allow the
copper and zinc to mix together to form brass.
This lab involves heating a solution of sodium hydroxide (NaOH). Be very
careful not to let the sodium hydroxide solution come into contact with your
skin. WEAR YOUR
GOGGLES AT ALL TIMES THROUGHOUT THIS LAB!
I.
Purpose: The purpose of this lab is to create brass, which
is an alloy (a homogeneous mixture) of copper and zinc.
II.
Procedure:
1.
Place 2 copper pennies
(each with a different minting year) in a 1.0M HCl
(hydrochloric acid) solution for 1-2 minutes.
Observe the chemical reaction that occurs as the oxidation is removed
from the penny.
2.
Remove the pennies
with crucible tongs and rinse with distilled water. Dry with a paper towel. Do not touch the pennies with your hands.
3.
Record the mass of
each penny.
4.
In a clean evaporating
dish, mix 1.0 g of granular zinc, your 2 pennies, and 25. ml
of 3.0M NaOH.
Cover the evaporating dish with a watch glass. Carefully heat the mixture until it begins to
steam and boil gently. Do not allow the
solution to boil too strongly!
5.
Continue to heat the
pennies in the Zn/NaOH mixture until the pennies are
completely coated with zinc. Move the
Bunsen burner away from the evaporating dish.
6.
Remove the coated
pennies from the Zn/NaOH mixture using the crucible
tongs and dip the pennies into a beaker of distilled water.
7.
Using the crucible
tongs, carefully and gently heat each coated penny in a Bunsen burner flame
until the zinc coating has mixed with the copper to form a brass penny. This only takes a few seconds!
8.
Dip each brass penny
into a beaker of distilled water. Dry
the penny and record its mass.
III.
Data: Create a data table showing your data
(and possibly the data of others).
IV.
Calculations: Determine the percentage of zinc in the brass
penny.