A standard solution is a solution that its concentration known accurately. Standard solution can be classify into two groups that is, a primary standard solution is a standard solution that prepared by dissolving an accurately weighed quantity of a highly pure substance and diluting to an accurately known volume in a volumetric flask.
A secondary standard solution is a solution that obtained from standardized a solution with primary standard solution. For example, sodium hydroxide is not sufficiently pure to prepare a standard solution directly and it is standardized by titrating a primary standard acid like such as oxalic acid. Oxalic acid is a solid that can be weighed accurately.
A primary standard should:
In acid base titration, hydrochloric acid is usually used as strong acid titrant for the titration of bases, and sodium hydroxide is the usual titrant for titration acids. Because none of theme is primary standard solution, so solutions of approximate concentration are prepared and then standardized with primary solutions.
Standard Base Solution
Sodium hydroxide is usually used as the titrant when base is required. Sodium hydroxide solution is usually standardized by titrating a weighed quantity of primary standard potassium acid phthalate (KHP), and a phenolphthalein end point is used.
Standard Acid solution
Hydrochloric acid is the usual titrant for the titration of base. Hydrochloric acid solution is usually standardized with primary standard sodium carbonate, methyl red is used as indicator and the solution is boiled at the end point because the end point is not sharp. Tris(hydroxymethyl)aminomethane is recommended as the primary standard unless the HCl is being used to titrate carbonate samples. If a standardized NaOH solution is an available the HCl solution can be standardized by titrating it with NaOH solution. Phenolphthalein or Bromothymol blue can be used as indicator.
A secondary standard solution is a solution that obtained from standardized a solution with primary standard solution. For example, sodium hydroxide is not sufficiently pure to prepare a standard solution directly and it is standardized by titrating a primary standard acid like such as oxalic acid. Oxalic acid is a solid that can be weighed accurately.
A primary standard should:
- High in purity
- Stable for drying temperature and stable in room temperature
- Readily available
- Have a high formula weight (but it is not necessary)
- React with the solution to be standardized directly
In acid base titration, hydrochloric acid is usually used as strong acid titrant for the titration of bases, and sodium hydroxide is the usual titrant for titration acids. Because none of theme is primary standard solution, so solutions of approximate concentration are prepared and then standardized with primary solutions.
Standard Base Solution
Sodium hydroxide is usually used as the titrant when base is required. Sodium hydroxide solution is usually standardized by titrating a weighed quantity of primary standard potassium acid phthalate (KHP), and a phenolphthalein end point is used.
Standard Acid solution
Hydrochloric acid is the usual titrant for the titration of base. Hydrochloric acid solution is usually standardized with primary standard sodium carbonate, methyl red is used as indicator and the solution is boiled at the end point because the end point is not sharp. Tris(hydroxymethyl)aminomethane is recommended as the primary standard unless the HCl is being used to titrate carbonate samples. If a standardized NaOH solution is an available the HCl solution can be standardized by titrating it with NaOH solution. Phenolphthalein or Bromothymol blue can be used as indicator.
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Mucorpepsin is an enzyme that catalyses the following chemical reaction: Hydrolysis of proteins, favouring hydrophobic residues at P1 and P1'. Clots milk. Does not accept Lys at P1, and hence does not activate trypsinogen. This enzyme is isolated from the zygomycete fungi Mucor pusillus and M. miehei. chymosin rennin
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