Answer 5 questions for all points Experiment 5 Experiment 5 - Standardization of
ID: 807041 • Letter: A
Question
Answer 5 questions for all points Experiment 5
Experiment 5 - Standardization of a Secondary Standard: 1 What is a primary standard? 2. List the characteristics required for a primary standard 9. A student measures the grams of oxalic acid needed to react with NaOH . He adds water to dissolve the add but did not swirl the solution sufficiently to completely dissolve the solid. He j? the sample of oxalic add with the NaOH in the buret. How would this affect the volume of NaOH needed to reach the end point of the reaction? What effect it will have in the molarity of the NaOH solution? Explain 11. A student completed the experiment and calculated the following molarities of NaOH. 0.09874 M. 0.1007 0.1012 M. will the student be within the 5ppt allowed for this experiment? Demonstrate with calculations of R.AD.Explanation / Answer
1)In order to determine the concentration of the sodium hydroxide solution, one must have an especially pure acid so that an accurately measured amount of acid can be weighed out on the analytical balance. The weight of this acid is the starting point for all subsequent calculations and it is therefore called the primary standard.
2) A primary standard should have the following qualities
: a. It must be easily prepared, purified and dried
. b. It must be stable and easily stored.
c. So it can be weighed in open air, it must not be hygroscopic. It must not react with any of the components of air such as carbon dioxide, oxygen or water.
d. Suitable methods must be available to test it for impurities. Generally, the total impurities must be less than 0.01-0.02%. The exact assay (i.e., the percent purity) must be known.
e. The reaction for which the primary standard is to be used must be quantitative and must be fast enough that it goes to completion in a reasonable period of time.