Preparation of chemical reagents
I. Purpose of the Experiment
A reagent is any substance in a chemical reaction. Different reagents are used for laboratory experiments depending on the nature and type of experiment.
II. Introduction
Concentration of a solution is the number of moles of solute present per litre of the solution. It can be expressed in terms of Molarity.
Molarity: The number of moles of solute dissolved in one litre of solution
Molarity= mol (Moles of solute) / L (Litre of solution)
Mole(mol) = mass (g) / Molar mass(g/mol)
Molar Mass (g/mol) : mass for one mole of any substance
III. Experimental
1. Chemicals: Sodium Hydroxide (NaOH) pellets, Sulphuric Acid solution
( H2SO4, 96%w/w, density 1.84 g/mL), Potassium Permanganate (KMnO4 crystals)
2 Equipment: Volumetric flask, Funnel, Watch glass, Spatula, Stirrer (Glass Rod), Polyethylene wash bottle, Reagent bottle, Measuring cylinder, Electronic Balance.
3 Procedure:
a. Preparation of approximately 0.1 M NaOH solution 1000mL.
- The empty watch glass was weighed by using electronic balance.
- Then approximately 4 g of NaOH added (poured) into watch glass which has the weighed
- Small amount of water was added to 100mL volumetric flask & NaOH pellets was poured through funnel into it.
- Funnel was removed. The solution was then swirled it until it became homogeneous. This will give a solution with approximately 0.1 M
b. Preparation of approximately 0.05 M H2C2O4. 2H2O solution 1000mL.
- 6.4g of H2C2O4. 2H2O crystals was placed on a watch glass and weighed again.
- Weighed H2C2O4. 2H2O crystals were poured to a volumetric flask using a funnel and small amount of distilled water was add to a volumetric flask by using a funnel.
- The glass stopper of the volumetric flask was placed and the mixture was then swirled thoroughly until all H2C2O4. 2H2O crystals were dissolved.
- Distilled water was filled up to the marking and was mixed by shaking. This will give approximately 0.05 M.
c. Preparation of approximately 0.1 M H2SO4 solution 1000mL.
- 5.4 mL of H2SO4 was measured with a measuring cylinder.
- H2SO4 was slowly poured through a funnel into the volumetric flask previously filled with 300mL of distilled water (made up the volume up to 1000mL and mixed it)
- A solution of H2SO4 will gave with approximately 0.1 M.
IV. Results and Discussions
(i) Molarity of NaOH solution......... 0.10M.
(ii) Molarity of H2C2O4. 2H2O solution......... 0.05M.
(ii) Molarity of H2SO4 solution......... 0.10M.
Discussion
1. What will you do, if the solution becomes hot while preparing NaOH solution?
I will pour cold water on the outer surface of the volumetric flask to cool it off
2. What will happen if distilled water is poured to H2SO4?
Heat is produced because the reaction is exothermic
3. What will you do if KMnO4 crystals are big and difficult to dissolve in distilled water?
Crush /grind them before adding in water to increase the surface area for dissolving.
V. Conclusion
Approximately 0.10 M NaOH solution, 0.05 M H2C2O4. 2H2O solution and
0.10 M H2SO4 solutions were prepared for further laboratory use.