In a student experiment, the empirical formula of a copper halide was found by a
ID: 821283 • Letter: I
Question
In a student experiment, the empirical formula of a copper halide was found by adding aluminum metal to an aqueous solution of the halide, displacing copper metal. The copper metal was filtered, washed with distilled water, dried, and weighed; three separate determinations were performed. The copper halide solution contained 42.62 g of copper chloride per liter. The student recorded the following experimental data.
What is the empirical formula for copper chloride based on the data results?
Trial Volume of copper chloride solution(mL) Mass of filter paper
(g) Mass of filter paper with copper
(g) A 49.6 0.908 1.694 B 48.3 0.922 1.693 C 42.2 0.919 1.588
Explanation / Answer
find the mass of copper in each trial and convert it to mass per liter
A) 1.694 - 0.908 g Cu / 0.0496 L = 15.847 g Cu / L
repeat for B and C
compare your three results
if they are fairly close, average them
if one is pretty far off the others you probably should discard that value
however, a glance tells me that your results should be tight
subtract the value for Cu from the value for the compound (42.62)
that gives the amount of chlorine
then
do a simple empirical formula calculation
I ran the numbers and got CuCl3 which surprised me because copper usually exhibits +1 or +2 oxidation state, but a quick check gave the possibility of +3 and +4 also