Chemical Reactions and Rate Influences

This assignment delves into the principles of chemical reactions and how various factors influence their rate. It examines the effects of temperature and concentration on reaction speed using examples like sodium thiosulfate reacting with hydrochloric acid and magnesium reacting with hydrochloric acid. Additionally, it explores the role of catalysts in speeding up reactions by providing alternative pathways with lower activation energies.

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CHEMICAL REACTIONS
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TASK 1: The Reaction between Hydrochloric Acid and Sodium Thiosulfate Solution
Sodium Thiosulfate reacts with dilute hydrochloric acid to produce Sulphur (IV) oxide,
Sulphur, and water. The Sulphur (IV) oxide gas produced is soluble and will completely dissolve
in an aqueous solution. The Sulphur, however, is insoluble and exists as a yellow precipitate
which mostly gives the solution a milky appearance (Kotz et al., 2012). This milky appearance
makes the mixture opaque, and the opaqueness can be used to measure the reaction rate. The
word and chemical equations below show what happens when sodium thiosulfate is added to
hydrochloric acid.
SodiumThiosulfate+ Hydrochloric Acid → Sulphur +Sodium Chloride+ Sulphur Oxide+Water
Na2 S2 O3 (aq)+2 HCl(aq)→ S (s)+2 NaCl(aq )+ SO2 ( g)+ H2 O(l)
Effect of Increasing the Temperature on the Rate of Reaction
Two separate test tubes of sodium thiosulfate and hydrochloric acid are placed in a water
bath controlled at a particular temperature. The two reagents are then added to a test tube, and a
stopwatch started, and the rate of reaction studied. This can be done by drawing a mark X on a
plane paper above which the beaker with the reagents is placed. The reaction is complete when
the mark is no longer visible.
From the experiment, it is evident that an increasing the temperature leads to an increase
in the rate of the reaction. This is because raising the temperature increases the energy of the
particles of the reagents thus moving around more quickly. The rate of the collision between the
particles thus increases which consequently increases the reaction rate. This reaction is a
precipitation reaction which forms a cloudy solution. As the temperature rises the speed at which

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the precipitates forms becomes faster thus the mark X disappears at a more rapid rate as
compared to when the temperatures are low.
The Effect of Decreasing the Concentration on the Reaction Rate
In this particular experiment, the goal is to investigate how the amount of concentration
affects the rate of reaction. The reaction is timed at the moment when the solution becomes
opaque, and the mark X becomes invisible. From the experiment, it is evident that the lower the
concentration, the slower the reaction rate thus the reaction takes more time to reach an
equilibrium. The phenomenon behind this reaction is that a dilute solution has fewer particles
that take part in the reaction. The frequency of collision thus becomes slower which in return
lowers the rate of reaction. If this happens, the mark X does not disappear fast. But in the case
when the concentration is more, the amount of colliding particles also increases thus increasing
the rate of reaction which results in a shorter time required to reach equilibrium (Huang, 2011).
This reaction employs the theory of collision.
In conclusion, it is evident from the above two experiments that increasing the
temperature will increase the rate of reaction and vice versa while reducing the concentration
also reduces the rate of reaction and vice versa.
The Reaction between Hydrochloric Acid and Magnesium Strips
Magnesium reacts with hydrochloric acid to produce magnesium chloride and hydrogen gas as
shown the equation below;
Mg ( s ) +2 HCl ( aq ) → MgCl2 ( aq)+ H 2(g)
The Effect of Increasing the Surface Area on the Reaction Rate

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From the experiment, it is clear that increasing the surface area of magnesium strips
increases the rate of reaction. This increase in reaction rate is because the amount of surface
exposed for collision with the acid is much more prominent. When the strips are cut into smaller
particles, the surface area is effectively increased. Thus more particles are exposed to the
reaction by the reactants (Henderson, 2013). The collision between particles rises which
effectively increases the rate of reaction.
The Effects of a Catalyst on the Rate of Reaction
A catalyst is a substance that can be used to speed up the rate of a reaction without
experiencing any chemical changes. During reactions, the reactants require a certain amount of
energy called the activation energy for the particles to collide. This energy is the minimum
energy necessary for the reaction to occur. To increase the rate of reaction, you need to increase
the amount of colliding particles, and this can effectively be done by using a catalyst to offer an
alternate path for the reaction to happen faster (Hagen, 2015).
From the diagram, the reaction pathway without the catalyst represented by blue shows
that the activation energy is high thus the reaction takes longer to reach equilibrium. On the other
hand, when a catalyst is added, a different reaction path is provided which is represented by red
in the diagram. This reaction path has lower activation energy, and thus the reaction reaches
equilibrium at a faster rate and thus forming the products. It should be noted that the catalyst
does not necessarily lower the activation energy but offers an alternative route for the reaction
(Hagen, 2015).
TASK 2
Effect of Temperatures and Concentration on the Rate of Industrial Reaction

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Temperature
In most industrial reactions, the rate of the reactions increases in direct proportionality
with an increase in the temperature of the reagents. Taking an example of the reaction between
sodium thiosulfate and hydrochloric acid, raising the temperature increases the vibration of the
particles of the reagents. This increase in the particle’s vibrations increases the rate of collision
between the reagents. The rise in collision efficiently increases the speed of reaction thus
equilibrium is achieved after a short time (Huang, 2011).
On the other hand, reducing the temperature lowers the vibration of the particles which
thus decreases the rate of collision between the molecules of the reagents. This in effect lowers
the rate of reaction thus taking longer to reach equilibrium.
Concentration
Increasing the concentration of the reagents implies that more particles are available for
collision thus increasing the reaction rate. Therefore, the higher the concentration, the faster the
reaction rate and vice versa (Kotz et al., 2012). Taking the example of the reaction of
hydrochloric acid with magnesium, increasing the concentration of the acid increases the rate of
reaction while reducing the concentration will lead to a reduction in the rate of reaction.

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References
Hagen, J., 2015. Industrial catalysis: a practical approach. John Wiley & Sons.
Henderson, P. ed., 2013. Rare earth element geochemistry (Vol. 2). Elsevier.
Huang, C.H., 2011. Rare earth coordination chemistry: fundamentals and applications. John
Wiley & Sons.
Kotz, J.C., Treichel, P.M., and Townsend, J., 2012. Chemistry and chemical reactivity. Cengage
Learning.