percentage yield Flashcards
5 factors that could reduce percentage yield
SIDE REACTIONS- unexpected reactions can happen. This may mean
that the intended product is not created.
WASTE- some of the chemicals will remain stuck to the glassware
and will be wasted.
INCOMPLETE REACTIONS- an incomplete reaction can happen
because:
-The reaction is very slow and hasn’t been
given enough time to happen.
-The reaction is reversible and some of the
products have turned back into reactants.
HYDRATION- If a reaction is carried out in water, any extracted
product may be ‘wet’
This means that there is water in the extracted
product. Water is generally extremely difficult to fully
remove from a product.If a percentage yield is
calculated to be over 100%, it is likely that your
product is full of water.
EXTRACTION- It might be difficult to fully separate the product from
the reaction mixture.
equation to calculate yield
The percentage yield of a reaction is calculated as the real yield divided by the theoretical yield multiplied by 100.
(real yield/ theoretical yield) x 100
A student wishes to collect the hydrogen evolved from a reaction between magnesium and hydrochloric acid.
They add 1.20 g of magnesium ribbon to 30.00 cm3 of a 1.5M solution of hydrochloric acid.
Suggest how the student might collect the hydrogen evolved and measure the volume?
Make sure to make specific references to the apparatus that you would use.
-Conduct the reaction in a conical flask.
-Add a bung to the top of the flask after adding the reactants.
-Connect the bung to a syringe so that the gas is collected in the syringe.
-The syringe will allow the volume of gas to be measured.
