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Practical investigation of the effect of temperature on therate of reaction of sodium thiosulfate with hydrochloric acid
Aim
The aim for this practical investigation is to understand how the rate of reaction changes of sodium
thiosulfate and hydrochloric acid by changing temperature each time, and to know how the speed of
the chemical reaction is affected by at the room temperature and by changing the temperature
(when heated)
Introduction
Reaction rate is the measure of how quickly the reactant in a reaction change into the product of the
reaction
Sodium thiosulfate and hydrochloric acid react to produce sulphur
Sodium thiosulfate + hydrochloric acid Sodium+ sulphur + sulphur dioxide
Na2S2O3 (aq) + 2HCl (aq) 2NaCl(aq)+S(s)+ SO2 (aq) +H2O(I)
aq=gas
s=solid
I=liquid
Research question
How does the temperature effect reaction rate?
Hypothesis
As we increase the temperature the rate of chemical reaction will increase and the time taken will
decrease.
Background
Collision theory is to explain how the different variables affect the rate of reaction, there are 4
factors that affect the rate of chemical reaction. These are concentration, surface area, catalyst and
temperature. In terms of collision theory when concentration increases, there will be more particles
and it makes the collisions more frequent, as the increases of the rate of reaction. Just like the
concentration a higher surface area will also increase the rate of reaction and they will have a higher
frequency of collisions. Catalyst provides an alternative pathway for the reaction with the lower
activation energy. Figure 2 explains the affect of catalyst on reaction rate. In our experiment the
concentration did not change but the temperature changes each time (we will do this experiment 3
times for each temperature) when the temperature increases the rate of reaction increase this is
because the particles will gain more energy which means they will be able to move faster, because
they move faster they will collide more frequently, a lot of collide with more energy each time, they
are more likely to exceed activation energy. Activation energy(see figure 3) is how much energy you
have to put into a system to have a chemical reaction occur, and it is based on collision between
molecules. There will be a higher rate of successful collisions, and a higher rate of reaction. All of the
factors will stay the same. The reaction is directly proportional because as we increase the
temperature between hydrochloric acid and sodium thiosulfate the rate of reaction will increase and
the time taken will decrease. The mixture will have more effective collision theory.
, Figure 1. Figure 2. Figure3
We can see from figure 1 when we have a low temperature the atoms are not moving fast, it takes a
lot of time for the atoms to chemically react and collide where as in the higher temperature they are
moving all over the place and they will bump into each other and react, we have more molecules in
the higher temperature so they will have more energy and they will be able to collide more
frequently.
Figure 4 shows Maxwell-Boltzmann distribution curve (T is the room temperature and T+t is at
higher temperature). As the temperature increases the amount of energy that particles have also
increases. At higher temperature, shifts have more collisions and they will have enough energy to
overcome the activation energy barriers and the kinetic energy of the molecules and the number of
the particles that have passed will increase. The area under the curve stays the same as the number
of particles stays the same. The molecules are moving faster when they have more kinetic energy at
a higher temperature. When the temperature increases at T+t more particles have the required
activation energy, more have enough energy to be able to have effective reaction, the more effective
collisions that take place so this will increase the rate of reaction. The lower temperature is shown in
blue whereas the proportion of molecules with energy greater than the activation energy at T+t. The
area altogether is increased and it is because they are more successful collision occur in a given time
and therefore the rate of reaction will increase.
Figure 4
When the temperature increases, the rate constant will increase and therefore the reaction rate will
increase too. So, there is another equation called Arrhenius equation which combines the theory of
the Boltzmann distribution law and activation energy into one of the important relationships in
chemistry.
K = rate constant
A = per exponential factor
e = base of natural logarithms
Ea = activation energy (J/mol-1)
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