Timeline for How to standardise NaOH?
Current License: CC BY-SA 4.0
15 events
| when toggle format | what | by | license | comment | |
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| Mar 29, 2019 at 6:23 | vote | accept | LXN | ||
| Mar 27, 2019 at 19:50 | comment | added | MaxW | I've asked the question about oxalic acid -- chemistry.stackexchange.com/questions/111646/… | |
| Mar 27, 2019 at 19:28 | comment | added | Poutnik | Hm, When I think about it , it would match rather HCl. HOx would be probably reversed, on the PhPht as well, as you suggested. | |
| Mar 27, 2019 at 18:56 | comment | added | Poutnik | In 80s, we titrated NaOH by HOx on methyl orange (3.1-4.4) I guess. When yellow showed hints of red, we stopped and heated the solution to strip it from CO2 from Na2CO3. Then we cooled it down. It turned back to yellow, but the red titration end was already close. | |
| Mar 27, 2019 at 18:35 | comment | added | MaxW | So what indicator would you use with oxalic acid when NaOH is the titrant? | |
| Mar 27, 2019 at 18:23 | comment | added | Poutnik | Phenolphthalein ( I am broking my fingers typing it ) . I apologize, it is a common abbreviation among Czech chemists, as we write it with F. I have forgotten that and it could confuse you. | |
| Mar 27, 2019 at 18:02 | comment | added | MaxW | I don't understand. What is "FF"? | |
| Mar 27, 2019 at 17:57 | comment | added | Poutnik | Using KHP with FF converts undefined amount of Na2CO3 to NaHCO3. | |
| Mar 27, 2019 at 17:38 | comment | added | MaxW | Using KHP and phenolphthalein works fine to standardize NaOH. For both KHP and oxalic acid you'd need to boiled distilled water to remove dissolved CO2 from atmosphere. | |
| Mar 27, 2019 at 17:19 | comment | added | Poutnik | Additionally, KHP is less suitable for the particular $\ce{NaOH}$ case, due its rather high $\mathrm{p}K_{a2} = 5.51$, compared to the $\ce{(COOH)_2}$ $\mathrm{p}K_{a2} = 1.27$ and $\mathrm{p}K_{a2} = 4.27$. As it would interefere with $\ce{H2O + CO2 <=> H+ + HCO3^-}$ ( of $\ce{Na2CO3}$ origin ) with the apparent $\mathrm{p}K_{app} = 6.35$ | |
| Mar 27, 2019 at 5:12 | comment | added | Poutnik | I mentioned oxalic acid as even since high school ( chemical industry oriented), not only in high school. The acid is used since a dawn of volumetric. In fact, I do not remember, if we ever used KHP for that purpose. | |
| Mar 27, 2019 at 4:38 | comment | added | Poutnik | It frequently used in universities and lab praxis as well.Potassium hydrogen phthalate is primary standard for pH. Hydrates are used often, if they are well defined. Another example of a hydrate standard is the Mohr salt $\ce{(NH4)_2Fe(SO4)2.6H20}$ for oxidimetry as a stable source of $\ce{Fe^{II}}$ | |
| Mar 27, 2019 at 4:25 | comment | added | MaxW | You might have used oxalic acid in high school, but potassium hydrogen phthalate (KHP) is the go to primary standard. You dry it in an oven before use. // I can't imagine a hydrate being used for serious work. | |
| Mar 27, 2019 at 1:59 | history | edited | Poutnik | CC BY-SA 4.0 |
added 145 characters in body
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| Mar 27, 2019 at 1:48 | history | answered | Poutnik | CC BY-SA 4.0 |