The Reaction of Copper (II) Chloride and Aluminum
Claim
A single displacement reaction occurs when a single metal displaces a less reactive
metal in a compound. The general form for this reaction is A + BC  B + AC, where A
and B are metals (Gallagher & Ingram, 2011). An example of a single displacement
reaction is when aluminum displaces copper from a solution of copper (II) chloride
to form copper and aluminum chloride, and is represented by the formula:
2Al + 3CuCl2  3Cu + 2AlCl3
The mass of an atom is determined by the number of protons and neutrons in the
nucleus of an atom, and is denoted the atomic mass on the periodic table (Gallagher
& Ingram, 2011). The atomic mass of aluminum is 27 atomic mass units (amu) and
the atomic mass of copper is 63.5amu. A single copper atom is 2.35 times more
massive than a single aluminum atom (Michael, 2011).
Evidence
Table 1: Finding the mass of copper produced from the reaction between aluminum
and copper (II) chloride
Finding the mass of aluminum
Mass of empty beaker
Mass of aluminum foil
Finding the mass of copper (II) chloride
Mass of empty beaker
Mass of copper (II) chloride
Finding the mass of copper
Mass of paper towel
Mass of copper
50.6g
0.6g
53.2g
6.0g
0.3g
2.1g
Reasoning
According to The Law of Definite Proportions, when two elements combine to form
a compound, they do so in a definite proportion by mass (Eisenkraft & Freebury,
2005). In the above reaction, 0.6g of aluminum produces 2.1g of copper, which tells
us that the copper produced is 3.5 times more massive than the aluminum
consumed. From the equation 2Al + 3CuCl2  3Cu + 2AlCl3 2 moles of aluminum
react to form 3 moles of copper. When the atomic masses of aluminum (27amu) and
copper (63.5) are multiplied by the number of moles in the balanced equation (i.e.
2x27 and 3x63.5), the same ratio of 3.5 is observed (Michael, 2011). This shows that
the Law of Definite Proportions holds true, and no matter what mass of aluminum is
reacted with copper (II) chloride, the amount of copper produced will be 3.5 times
more massive (Eisenkraft & Freebury, 2005).
A colour change was observed in the above reaction. The reactants in the reaction
were aluminum and copper (II) chloride. This is a single displacement reaction, and
aluminum displaced copper from the compound to form the single element copper
and a solution of aluminum chloride. A change in colour was observed, as copper
was formed when it was displaced by aluminum (Gallagher & Ingram, 2011; Walker
Waugh, n.d.).
Rebuttal
From the reaction 2Al + 3CuCl2  3Cu + 2AlCl3, there would not be more aluminum
consumed that copper prodcued because copper is more massive than aluminum.
The mass of a single aluminum atom is 27amu and the mass of a single copper atom
is 63.5amu (Michael, 2011). The balanced chemical equations shows that 2
aluminum atoms react to form 3 copper atoms, which shows it would be impossible
for aluminum to be more massive than copper.
The aluminum did not stay the same colour, because a single displacement reaction
was observed. Aluminum replaced copper in the copper (II) chloride solution,
forming copper and aluminum chloride. Aluminum is a silver colour and copper is a
redish-brown colour.
References
Eisenkraft, A. & Freebury, G. (2005). Active Physical Science: An Inquiry Approach to
Physical Science. Armonk, NY: It’s About Time, Herff Jones Education Division.
Gallagher, R. & Ingram, P. (2011) Complete Chemistry for Cambridge IGCSE. Oxford, UK:
Oxford University Press.
Michael, D. (2011). Ptable. Accessed October 3, 2012. Retrieved from
http://www.ptable.com/
Walker Waugh, M. (n.d.). Santa monice college. Accessed October 3, 2012. Retrieved
from
http://homepage.smc.edu/walker_muriel/single_replacement_battery_lab_procedu
re.htm