Rate of Reaction of Dilute Hydrochloric Acid and Sodium Thiosulphate
To investigate the change in rate of reaction between DILUTE HYDROCHLORIC
ACID and SODIUM THIOSULPHATE as the concentration varies.
A chemical reaction takes place over a specific period of time i.e.
which is the time for the reactants to be formed into the products. If
the reactants take a relatively short time to form the products, the
reaction is known as a FAST one. The RATE of that particular reaction
is high. On the other hand, a reaction which takes a longer time is
known as a SLOW reaction, and as a result is known to have a LOW rate
There are several factors which alter can ...view middle of the document...
So, in other words,
they reduce activation energy levels. A catalyst works by increasing
the chances of particles colliding by providing a ‘sticky’ surface on
which particles stick onto and have a collision. Therefore the greater
the size of the catalyst, the higher the rate of reaction.
Constant: A catalyst won’t be used in our experiment.
PARTICLE SIZE- Obviously, as the surface area of a reactant increases
(solid), there is more space for particles to work on and react, and
therefore this results in more reactions.
Constant: As no solid is involved in our experiment, the particle size
theory doesn’t matter.
LIGHT- Some chemical reactions are speeded up with light, and not only
with heat. For example, silver is formed from silver salts when a
photographic film is exposed to light. On the other hand, green plants
absorb sunlight for photosynthesis, and the more that is absorbed, the
higher the rate of reaction.
Constant: Light is irrelevant to our experiment, so there need not be
any control over it.
PRESSURE- Pressure applies only to reactions between gases, and as the
pressure increases, so does the speed of the reaction. The reason
behind this is that increasing the pressure pushes the gas molecules
closer towards each other, and so increasing the chances of the gas
particles colliding, causing the reaction to take place at a faster
Constant: Pressure is inappropriate to our experiment as no gases are
involved, rather liquids.
In this investigation, we shall be investigating the effect of changes
in concentration on the rate of reaction, and the two chemicals which
shall be used will be Sodium Thiosulphate and Hydrochloric Acid.
Another point to make is that in order to keep the experiment fair,
the ‘cross’ must be kept the same. The easiest way to do this is to
use the same cross for the entire experiment, or else the results
would go unwittingly wrong. A thicker cross on a different paper in
the same experiment would take longer than normal to ‘disappear’,
whereas a thinner one would take a shorter amount of time, so it’s
very important to keep it the same.
I predict that the greater the concentration of one of the solutions,
whilst the other remains constant, the greater the rate of reaction.
This is because, as explained by the collision theory, in a more
concentrated solution, the ions are closer together because they exist
in a greater number. Therefore, the closer they are to each other and
the higher their numbers, there is a greater chance of successful
collisions, and when there is a greater chance of collisions taking
place, there is a greater chance of a reaction occurring and therefore
the reaction should take place quicker.
Where there are more particles in a confined zone, such as the beaker,
there will be more collisions between them. This results in more
reactions taking place, which in turn increases the rate of reaction.