March 24, 2017

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1. Why cannot NaOH be used as primary standard for HCl?
2. Aside from carbonates, what other compounds can be analyzed using the double indicator method? What are the requirements for a sample to be analyzed using the double indicator method?
3. what is a carbonate error? Explain the cause of carbonate error and its effect on the calculated values obtained in standardization and sample analysis.

1. Even if we could buy PURE NaOH, it wouldn't stay that way due to absorbtion of CO2 from the air. That portion of CO2 would make Na2CO3. So the NaOH must be standardized using a primary standard such as potassium hydrogen phthalate.
2,3,and 4. I'm sure all these (including #1) are discussed in your text. I shall be happy to critique your thoughts.

for my second question, my idea is that double indicator method is applicable to all polybasic compounds. Is this true? If this is, then double indicator method is applicable to phosphates, oxalates, sulfates, arsenates, etc. Am I right?
As for my third and fourth question, I really have no idea about carbonate error. What is this all about. I have tried searching for an answer in the internet but I can't find any explanations about this error.

Second Question:

BTB works. PH Paper

The double indicator method is applicable to selected mixtures and selected dibasic and/or tribasic acids.
What text are you using and what course are you taking? Perhaps I can tell you what to read.

I am using "Fundamentals of Analytical Chemistry" by Skoog, West, Holler and Crouch. I am a Chemistry major

I suspected that but I wanted to confirm to make sure.
Look in the index under "sodium hydroxidei solutions, preparation and standardization of". Within that section that is a subsection on "The Effect of carbon dioxide upon standard base solutions." My copy of Fundamentals of Analytical Chemistry by Skoog, West, and Holler is the sixth edition; threrefore, I can't give you the exact page. However, my copy also has "carbonate error" listed in the index. For answers to double titrations etc look in the index under "Carbonate-hydrogen carbonate mixtures, analysis of". In that section there are a number of side column notes and references to figures in chapter 11 that talks about the mixtures that may be separated and some of the problems associated with them. Your text and mine won't have the same page number or perhaps not even the same chapter number; however, all of the answers you seek are in those sections I noted. Post specific questions but tell us exactly what you don't understand about them.

Thank you very much DrBob22!!!

From UP Diliman kb?

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