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Preparing a standard solution


After calculating the mass of solute that
you need you can then weigh this into a weighing boat using a top pan balance. You should use an appropriate balance
probably one to two or three decimal places. After weighing the solute can then be
transferred into a glass beaker and it’s important to make sure that all of the
solute is transferred and to do this you should rinse the weighing boat with
distilled water. You now need to ensure that all of the
solute has been dissolved in distilled water. So you should add more water if required
and you should swirl the solution. You may also need to use a glass stirring
rod. Once you are happy that all of the solute is
dissolved you can transfer your solution into a volumetric flask using a glass
funnel. Take care not to spill any solution
because if you do so you will have to start the whole process again. Now it’s vital to rinse the beaker to
ensure that none of your original solution is left behind. You will be required to do this a number
of times and if you’re not sure what the guidelines from your teacher are, ask
how many times you should do this. In any case, it should be two or three times and
having rinsed the beaker it’s also important to rinse the glass funnel to make sure
that none of the original solution is left in there either. Once you’re happy with the rinsing you
can remove the funnel and place a stopper into the volumetric flask and gently shaking the flask at this stage ensures that all of the solute is in solution and is easier to do than when the flask has been topped up with water and now we’re ready to fill the flask up to
the line. This can be done using distilled water
from a wash bottle. As you get closer to the line it’s important to take great
care because if you overshoot you’ll have to start the whole thing again. When you’re within a couple of
centimetres of the line make sure your viewing at eye level and add the water very
slowly in small portions until the bottom of the meniscus is touching the
line. You may want to use a dropping
pipette at this stage if you’re a little nervous and here you can see that the bottom of
the meniscus is touching the line. So we have filled the flask to the correct
level. Once the solution is made up it should
be stored with a stopper firmly in place and before using the solution you must
ensure that it is homogeneous, which can be done by gently inverting and shaking
the flask. We now have a standard solution, which is
ready to be used in a titration.

Reynold King

6 Replies to “Preparing a standard solution”

  1. At around 3:00 – 3:05, one can quite clearly see the double line in the neck of the flask, indicating that the viewer is not looking perfectly horizontally through the neck of the flask, and hence giving rise to parallax error. This should be avoided, and it should also be pointed out, as it gives rise to determinate error.

  2. pay attention to the liars the only laboratory aggregated by the AfDB is in Algeria its customer service responds to 00213 541475850 all the rest is scammers and I have my proofs it work on percentage [email protected]

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