Conclusion
From my results it shows that my predictions are right and
my result shows that as the concentration of HCl acid
increases the rate of reaction increases as well. And apart
from some results, all my points fit into the line of best
fit, meaning the points are in a line going up and I can
say that my prediction is right because I said that the
concentration increases by a certain number all the time
and so the line will go straight up. We can explain this by
using the collision theory, because it states that as the
concentration increases by a certain number, meaning the
amount of HCl particles in a certain volume will increase,
if the concentration of HCl was increased and this would
result in the increase of collisions between the HCl
particles and the Mg particles because the particles would
be more crowded together, meaning cause for a faster rate
of reaction. If we increase the concentration further, we
are adding more HCl particles, which means that the rate of
reaction will increase as well. The collision theory also
states that the only way for two different substances to
start reacting with one another is by coming in contact
with each other. And in order to do this the particles must
have enough energy to react, we call this a collision when
two particles come together and react. This is because the
particle electrons would repel each other when they come in
Higher Concentrations
Lots of collision
A faster reactions
Lower Concentrations
Fewer collision
A slower reactions
HCl
Mg
contact at a low speed and energy; therefore we need the
particles to collide with each other to start a reaction.
This means that particles need a lot of energy or a certain
amount of energy to penetrate the repelling force of the
electrons and to cause a successful collision. We call this
energy ‘the activation energy’. Concentration affects the
rate of reaction because as the amount of HCl particles
increase in a given volume, it starts to get crowed. So the
number of successful collisions in one time would happen
more and the chances of a successful collision increase,
this is why we get a faster reaction rate.
This agrees with my prediction because I predicted
that the rate of reaction graph would go straight up and
looking at graph 1 it does go straight up but what don’t
agree is that the line of best fit start at “0”. I also
predicted that as the concentration increased the rate of
reaction increased every 0.5cm³ but it didn’t but was very
close to 0.7cm³. We can tell that hydrogen gas was given
off because we tested some of the sample collected when the
reaction started and used the “pop test” which is the test
for hydrogen gas and the sample went pop meaning hydrogen
was present.
From the graph I can conclude that as the concentration
increases by 0.25 molar on my line of best fit, the rate of
reaction increases by 0.7cm³/s. This means in the control
of normal room temperature (23C), 40ml of HCl acid and 4cm
magnesium strip, the increase of concentration by 0.25
molars results in the increase of 0.7cm³/s.
From the graph, which shows the time taken for 20cm³
of gas to be collected, shows clearly that as the
concentration increases, the time taken to collect 20cm³ of
gas will decrease, meaning a faster collecting time.
Observing both graphs the collecting gas time graph, isn’t
a straight line of results but a curve, which decrease in
gradient as the concentration increases and the gradient on
the curve gradually gets shallower. This agrees with my
prediction and the reason for this is because at the start
of the concentration increase there was a small number of
HCl to react with the Mg particles at one time, meaning a
slower time taken to collect the gas and a big difference
of time taken is shown. But further increase of
concentration didn’t make a big difference in the time
taken to collect gas, after the concentration of 1.25
molars because there is enough HCl particles to react with
each Mg particles now and a few extra HCl particles can
react with the Mg. An increase in concentration wouldn’t
make much of a difference because only a few numbers of
particles can react with the Mg at one time.
We get this Hydrogen gas because when the Mg particles
react with the HCl solution (containing Cl - ions and H+
ions) we see some sort of displacement reaction going. The
Cl - ions reacts with the Mg as it collides with the Mg
particle because Mg is higher in the reactivity series than
Hydrochlor ic acid  Magnesium 
 Magnesium Chloride  Hydrogen
Hydrogen (H2) and the Mg displaces the H+ ion and the Cl –
ions and Mg form Magnesium Chloride (MgCl2): -
Now there are isolated H+ ions around the solution. These
2HCl  Mg  MgCl2  H 2
H+
isolated
ions react with other isolated H+ ions to form H2
gas, but cannot because they don’t have any free electron
on there outer shell. This means they need extra two
electron. The extra two electron are gain from the Mg this
is because when Cl - ions reacts with the magnesium it
already has a full outer shell, meaning when the Mg reacts
with the Cl - ions there are free two electrons. The H+ ions
HCL

 H 
  H   2e 
H2

2e 
Cl 
  Mg
MgCl 2
get attracted to the free electron and form full hydrogen
atoms. These hydrogen atoms are diatomic so they must be in
pairs, so the hydrogen atoms react with other hydrogen
atoms and become H2 atoms. Below is a diagram showing what
happens to each individual ions: -