My friends and I did it together, we also looked over it with a science teacher with a degree in chemistry and she said it was worthy of a distinction. PS: Don't copy word for word ;)
FACTORS THAT INFLUENCE PURITY
In all the experiments we carried out, there was always room for errors and problems that could
affect the % purity of our end products, which is why it is important that we followed the steps
properly and efficiently.
In every experiment we recrystallized our products to ensure purity. During the
recrystallization process, if too much water is added to the solution, the mass of
the product to decrease but the more water you add, the less the impurities you
will have left after the recrystallization process. However, if you add too little
water, there would be impurities remaining in the solution after drying it. So it is
important to a moderate amount of water during recrystallization to influence
purity.
Another case where the purity of the product could be affected is after recrystallization. Before
measuring the mass of our product, we had to let it dry and cool. This sometimes can affect the
purity because if the filtrate is left for too long in the evaporating basin, the mass of
the filtrate would decrease. Also when allowing it to dry, we used tissue to dry our products in
the evaporating basin. The tissue may have contained impurities and could cause contamination
which can affect the % purity.
Another factor that influences purity is having an inconsiderably excess amount of a reactant. When
there is an excess amount of a reactant, it would lead to that reactant being present at the end point
of the reaction. This affects the purity of the end product and other values because an undesired
product is formed. This can also cause unexpected side reactions greatly which end up affecting the
purity of our products. These side reactions are caused because the excess reactant triggers a
reaction with a compound that may be present in the container before the reaction begun. This is
due to contamination present in the equipment and can be avoided by using clean equipment.
While performing our experiments, it was very easy for our samples to get contaminated which
would affect the % purity. Especially the equipment (beakers, filtrating funnels, stirring rods, etc.) we
used during our experiments, because they may be contaminated from previous experiments and
were not cleaned properly after use. Even when we left our sample to dry by the window, dust
particles would have been able to come in and contaminate them. These substances that
contaminate our product may react with the reactants during a reaction and produce unwanted side
reactions. This really affects the purity of the products and affects other values such as mass and
atom economy.
Equilibrium can also affect purity. Equilibrium is the state in which both the
reactants and products are present in concentrations which have no further
tendency to change with time. This means the products are forming just as fast
as they are converted back to the reactants. The rate of conversion is balanced.
Because we can’t really tell when the equilibrium changes, this can cause us to
take away our product too early allowing some reagents/impurities to be present
in the final product. So therefore, not all the reactants in this reaction formed the
product and this affects the purity of the product because impurities still remain
in them.
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