The experiment was designed to review stoichiometry, introduce common statistical methods for
analyzing data, conduct a simple inorganic synthesis, and review accuracy and precision in a lab.
A-1, the weights of supposedly identical washers galvanized with zinc were recorded; one washer, the
master washer, was weighed on five separate balances to compare the average to the true value of the
provided washers, which is 5.2 g, and its dimensions were also taken (total radius 25.5 mm, inner radius
11.5 mm, height 1.5 mm).
The percent error for the master washer, which had an average mass of 5.196
g, was 0.08% [A-1], and the standard deviation was 0.009; thus, the balances were accurate and precise,
because the masses were close and the total average was close to the true mass of a washer.
were weighed on the same balance, which produced an average value of 5.361 g and a standard deviation
of 0.151, which is not as precise as the master washer but still fairly precise. As a result, weighing one
washer on five different balances is more accurate and precise than weighing five washers on one balance
Next, the master washer was placed in a 3 M solution of HCl until the reaction completed, in order
remove the zinc coating from the washer.
If the washer was removed before the reaction went to
completion, the corresponding zinc thickness calculations would yield a result smaller than desired,
because the amount of removed zinc would be less than the actual value of the completed reaction [A-2].
Once the reaction was completed, the mass of the master washer was recorded (5.177 g), which revealed