Before you carry out your titration you'll need to make up a standard solution,
that's the solution of a known concentration.
In this case we'll be
making up a solution that's about 0.1 mol/dm3 sodium carbonate
in a 250 cm3 volumetric flask.
In this video we'll run through the steps required to make up your standard solution,
including all of the measurements and calculations you'll need
to carry out to get the exact concentration of your sodium carbonate solution.
To make up the standard solution, it's necessary to know accurately the exact
mass of sodium carbonate, which will be dissolved in a known volume of water.
The best way to do that is by a method called weighing by difference.
Using a spatula, measure out approximately 2.6 grams of anhydrous sodium carbonate.
Record the mass of the sodium carbonate with the weighing boat.
Transfer this solid to 100 cm3 cubed beaker.
Re-weigh and record the mass of the used boat.
Using these measurements, you can calculate the exact mass of anhydrous sodium carbonate.
Next, take this anhydrous sodium carbonate
and dissolve in distilled water from a wash bottle.
Stir this solution thoroughly until the solid is completely dissolved.
For the next step, you'll need a 250 cm3 volumetric flask,
and a funnel.
Pour your solution down a glass rod and
through the funnel into the flask.
Make sure to raise the funnel, so that it drains smoothly.
To make sure all of your sodium carbonate solution is transferred
to the volumetric flask, you should use a wash bottle to rinse the beaker.
Make sure to add this rinse to the volumetric flask each time,
and do this at least three times.
Take care as well to only use a small amount of water,
so as to not go higher than the 250 cm3 mark
on the volumetric flask.
The same should also be done with the funnel.
Add distilled water to the 250 cm3 mark.
Take care to observe the meniscus at eye level,
rather than from above or below.
To make sure the concentration of anhydrous sodium carbonate is the same
throughout your solution, stopper the flask
and gently invert it several times.
Finally, you will need to label the flask clearly
including the exact concentration of your solution.
To calculate the concentration of your standard solution,
you first have to work out the molar mass of anhydrous sodium carbonate
as shown here.
To calculate the amount of substance used, you will then have to divide the
mass of the anhydrous sodium carbonate used by its molar mass.
As we know the volume of the solution in the volumetric flask is
250 cm3, we can calculate the concentration.
Remember to divide by a thousand to convert the units of volume
from cm3 into dm3.
So, the known accurate concentration of your sodium carbonate solution is
therefore 0.0974 mol/dm3.