Erika Lu
2A
Single Replacement Reactions Lab
Problem
What reaction will happen when a metal combines with an acid?
Hypothesis
If a metal meets with an acid, then the metal could replace the hydrogen atom in the
acid, giving off the replaced hydrogen. Therefore, there will be bubbling due to the
hydrogen gas being released.
Independent/Control variable: metals
Dependent variables: acids
Experimental Method
The metals were placed into separate wells. Then each acid was added to each type of
metal. Observations were made after two minutes. The plate was left at room
temperature for two days, then observed again.
In preparation for the lab:
1. Safety requirements are followed. Gloves, aprons, and safety goggles will be used
when conducting the experiment.
2. A table is created to record the information.
3. Research is done to determine what kind of evidence to look for when conducting
and observing the experiment.
Background Info:
Single Displacement: This is when one element trades places with another element in
a compound. These reactions come in the general form of:
A + BC ---> AC + B
One example of a single displacement reaction is when magnesium replaces hydrogen
in water to make magnesium hydroxide and hydrogen gas:
Mg + 2H O ---> Mg(OH) + H
2
2
2
In a single replacement reaction, there is a rule that is always followed. A metal
replaces a metal, or a nonmetal replaces a nonmetal.
Procedure Data Collection
Elements
Observations
Evidence
Al + HydroChloric
The piece of metal has bent
completely in half.
Endothermic, we could feel
the heat. It was bent.
Zn + HydroChloric
Little bubbling, halfway through
the experiment.
The piece of metal turned
black-ish.
Cu + HydroChloric
No reaction the first day, but when
we came back, water was blue.
The acid turned blue and the
piece of copper turned black. It
is very flimsy and flexible
now.
Mg +
HydroChloric
The metal has started to bubble
and it is letting off a gas. White
bubbles are rising to the surface
and the bubbling is not stopping.
Burning smell. It is making a
"whoosh" sound.
It completely dissolved.
Nothing is left.
Elements
Observations
Evidence
Al + Nitric
No Reaction.
After two days: some small
pieces came off and the sides
are brown.
Zn + Nitric
There are bubbles around the zinc.
After two days: the piece of
metal turned black.
Cu + Nitric
No Reaction.
No Reaction.
Mg + Nitric
There are bubbles around the
magnesium.
After two days: the metal
turned black on the sides.
Elements
Observations
Evidence
Al + Sulfuric
The piece of aluminum is slowly
folding.
The metal has bent. It is
endothermic.
Zn + Sulfuric
Bubbles are holding onto the piece
of zinc.
It looks the same but bubbles
are still holding onto the zinc.
Cu + Sulfuric
No Reaction.
No Reaction.
Mg + Sulfuric
Fizzing. Smoke is coming out.
Burning smell. "Whoosh" sound.
The metal is bending. It is turning
white.
It has somewhat dissolved.
The piece of metal turned
white. It looks like dust on the
metal.
Data Processing
Using the single replacement formula:
A + BC --> AC + B
We can conclude that the balanced chemical results of the experiment are:
Magnesium
after
hydrochloric
was added
2 Al + 6 HCl --> 2 AlCl3 + 3 H2
Zn + 2 HCl --> ZnCl2 + H2
Cu + 2 HCl --> CuCl2 + H2
Mg + 2 HCl --> MgCl2 + H2 2 Al + 6 HNO3 --> 2 Al(NO3)3 + 3 H2
Zn + 2 HNO3 --> Zn(NO3)2 + H2
Cu + 2 HNO3 --> Cu(NO3)2 + H2
Mg + 2 HNO3 --> Mg(NO3)2 + H2
2 Al + 3 H2SO4 --> Al2(SO4)3 + 3 H2 Zn + H2SO4 --> ZnSO4 + H2
Cu + H2SO4 --> CuSO4 + H2
Mg + H2SO4 --> MgSO4 + H2 Nitric acid
two days
after
addition of
copper
Left: aluminum
Right: aluminum
after sulfuric
acid was added
Coefficients had to be changed in order for the equations to be balanced. This is due
to the Law of Mass Conservation, which states that matter is neither created nor
destroyed during a chemical reaction, and therefore there must be the same number of
atoms on each side of the equation.
In this case, the reactants are the metals (Al, Zn, Cu, Mg) and the acids (HCl, HNO3,
H2SO2). The data appears to show that the metals in order from most reactive to least
reactive are magnesium, zinc, aluminum, copper. The hydrochloric was the most
reactive acid while the nitric was least reactive. The most reactive combination was
hydrochloric acid with magnesium.
Evaluation
Conclusion:
My hypothesis was that a reaction of the acid combining with the metal will
be bubbling. My results appear to support my hypothesis.
Evaluation:
From my experiment, I see that when a metal combined with an acid, the
metal replaced the hydrogen in the acid compound, giving off the hydrogen in the
form of bubbles. The combination of magnesium with hydrochloric acid was the most
reactive. There was much bubbling until the magnesium completely dissolved within
minutes. There was no magnesium left, indicating that a chemical change has
occurred because a new substance had been formed. The unbalanced formula is Mg +
HCl --> MgCl2 + H2. The magnesium combined with the chlorine to form a new
compound, while the hydrogen broke off to be by itself, which could be visibly seen
in the bubbles. However, while the magnesium quickly dissolved, the copper showed
no reaction with the nitric and sulfuric acids. With the hydrochloric, the piece of
copper took two days for any change in appearance to be visible. The acid was turned
blue and the copper was turned black. This shows that with copper, single
replacement takes longer than with magnesium.
There are many possible errors that could have occurred in the experiment.
We may have accidentally added different amounts of acids each time that could have
possibly altered the results. The forceps we used may have contained traces of other
chemicals that may have resulted in the mixing of the acids. Also, in some cases the
metals were difficult to remove with forceps, and much prodding was done. In other
cases, the metal was hardly touched. This could have affected the results.
Improvements on this experiment could be to count exactly how many drops of acid
are added, and to cut pieces of metal to exactly the same mass. It would also be
helpful to record the time of observations – whether it was two minutes later, half an
hour later, or a day later.