Lecture notes Unit 2 Assignment 1 BTEC Level 3 National Applied Science Student Book, ISBN: 9781846906800
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BTEC Level 3 National Applied Science, Student Book
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Keeping the Standards
Unit 2 Assignment 1
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UNIT:2
TITILE: Keeping the Standards
Heather Weston
Anmolpreet Kaur
♦ Part 1 Preparation of a standard solution
Aim: The purpose of this experiment is to a prepare a standard solution of
sodium carbonate and finding the concentration of the solution.
Introduction: A standard solution is a solution with a precisely known
concentration that is created up to a defined volume from a primary standard
(a substance that is stable of high purity, highly soluble in water, and has a high
molar mass to allow for accurate weighing). Standard liquid solutions, such as
acids, are simple to make and are often available. By weighing a mass of solid
and dissolving it in a known volume of solution in a volumetric flask, standard
solid solutions can be made. In this experiment I will make a typical sodium
carbonate solution that I will utilise in a later practical (Standardisation of an
acid). Standard solution can also be used as titration which is used se to find
out the concentration of other solutions. https://edu.rsc.org/resources/standard-
solution/2257.article
Equipment:
1. Weighing Balance
2. Large Beaker.
3. Spatula
4. Distilled Water
5. Volumetric flask
,6. Anhydrous Sodium Carbonate
Procedure:
To begin, I calibrated the weighing balance by turning it on and making sure it
was level, after which I placed a weighing boat on top of it and pressed '0' to
verify that all my measurements were precise.
I weighed out around 1.35g of anhydrous sodium carbonate and after this
procedure the sodium carbonate was then carefully moved to a large beaker,
and all measurements were meticulously documented to ascertain the exact
mass transferred.
After this I added 150cm3 of distilled water to the beaker and stirred it with the
spatula until I had completely dissolved the sodium carbonate, once it had all
dissolved, I carefully and accurately transferred all the solution to a 250cm 3
volumetric flask and made up the solution to 250cm 3 with more distilled water.
Calculations:
How to work out the concentration of a solution – CONCENTRATION =
Number of moles⁄Volume ⁄1000
1.First, I worked out the number of moles in sodium carbonate (Na 2CO3)
→ Na⨉2 (23⨉2 = 46)
→ C⨉1 (12⨉1 = 12)
→ O⨉3 (16⨉3 = 48)
→ = 106
2.Now, how to work out the number of moles: I used the equation:
→ MOLES = Mass⁄Mr
→ Moles = 1.35⁄106 = 0.0127
→ Moles = 0.0127
After I have worked out the number of moles I than worked out the
concentration of the solution, knowing the number of moles is 0.0127 and the
volume is 250cm3.
Final Step The concentration of the is calculated as
, → 0.0127⁄250⁄1000 = 0.0000508mol/dm3
→ (Results may vary with other students results as we all may have used
the different amounts of anhydrous sodium carbonate.)
Results of Sodium Carbonate: In part 1 I produced a standard solution of
sodium carbonate (The disodium salt of carbonic acid with alkalinizing
properties is sodium carbonate. When sodium carbonate is dissolved in water,
it produces carbonic acid and sodium hydroxide. Because sodium hydroxide is
a strong base, it neutralises gastric acid and so acts as an antacid.)
https://pubchem.ncbi.nlm.nih.gov/compound/Sodium-carbonate
Evaluation: When I was doing the experiment some of the sodium carbonate
was spilled when transferring so that is why the concentration of sodium
carbonate will record a lower value than its true value because by n = m⁄M ,
since mass decrease, the number of moles of Na2CO3 will decrease, then the
concentration of the Na2CO3 is calculated by (number of moles of Na2C03 ⁄
Volumeof solution) so that when no of mol Na2CO3 decrease, the
concentration will decrease.
After I finished the experiment, I realised that every step is particularly
important in preparing standard solution. If I have missed some of the steps,
the concentration of the solution can be affected. For e.g. While I am weighing
the sodium carbonate therefore the top the balance may contain some Na2CO3
so it is my responsibility to clean the solid on the top of the balance first to get
an accurate experiment done. I also need to wash the beaker 3-4 times to
make sure all the sodium carbonates have travelled into the volumetric flask.
Our eye level must be same as the graduation mark while adding the water to
the graduation mark. To distribute the Na2CO3 solution equally in the
volumetric flask I need turn the flask upside down.
Conclusion: The concentration of the standard solution is 0.0000508 mol/dm3.
Diagram: http://chemaddicts.blogspot.com/2015/10/how-to-make-primary-
standard-sodium.html
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