I'm doing Chemistry 3.1 and as part of my chosen investigation I need to have standardised NaOH and standardised HCl.
I want to standardise HCl with a primary standard (sodium carbonate) and then standardise NaOH with this HCl. The only method I could find on the internet for standardising NaOH with HCl said to put phenolphthalein in the NaOH, bu this would make it purple!!! That can't be right, because how would I easily find the endpoint if I titrated clear HCl into a purple solution? So instead the base needs to be in the burette and the acid in the flask - is this okay to standardise the base? Is there a rule about which solution goes where, for example does the solution being standardised have to be in the flask?
Or would I not use phenolphthalein?
If I can't standardise NaOH with HCl then my only option is to use oxalic acid to standardise HCl to standardise NaOH, but I would much prefer to go the other way and use sodium carbonate to standardise HCl to standardise NaOH.
I would appreciate some help from someone who is familiar with Level 2/3 Chemistry (high school chemistry) and if possible a link from a website for a method would be helpful.
I want to standardise HCl with a primary standard (sodium carbonate) and then standardise NaOH with this HCl. The only method I could find on the internet for standardising NaOH with HCl said to put phenolphthalein in the NaOH, bu this would make it purple!!! That can't be right, because how would I easily find the endpoint if I titrated clear HCl into a purple solution? So instead the base needs to be in the burette and the acid in the flask - is this okay to standardise the base? Is there a rule about which solution goes where, for example does the solution being standardised have to be in the flask?
Or would I not use phenolphthalein?
If I can't standardise NaOH with HCl then my only option is to use oxalic acid to standardise HCl to standardise NaOH, but I would much prefer to go the other way and use sodium carbonate to standardise HCl to standardise NaOH.
I would appreciate some help from someone who is familiar with Level 2/3 Chemistry (high school chemistry) and if possible a link from a website for a method would be helpful.
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By far and away, the preferred method is to use potassium hydrogen phthalate (KHP) as the primary standard to standardize the NaOH solution. Then use the standardized NaOH to standardize the HCl solution.
If you insist on using oxalic acid, then that can only be use to standardize the NaOH(aq).
If you insist on using oxalic acid, then that can only be use to standardize the NaOH(aq).
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NaOH is usually standardized with KHP, potassium hydrogen phthalate. Then use the standard NaOH to titrate HCl but use the NaOH solution in the burette and pipette the HCl into the reaction flask with the phenolphthalein indicator.
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As the other answerers have indicated , KHP is the usual standard for NaOH. But, if you really want to standardize the acid with NaCO3, just be sure you use a freshly made NaCO3 solution to avoid effects from absorption of atmospheric CO2.
Then, you can do what is called a back titration to standardize your NaOH. Pipette a known amount of HCl into your titration beaker and then add the phenolphthalein. Add the NaOH from your burette until you get your color change. If you get a color change right away, increase the amount of HCl so that you get a more gradual color change. If you add a whole burette of NaOH and get no color change, cut the HCl in half and dilute to the same volume and titrate. Repeat until you get a definite end point and then calculate based on your knowns.
Then, you can do what is called a back titration to standardize your NaOH. Pipette a known amount of HCl into your titration beaker and then add the phenolphthalein. Add the NaOH from your burette until you get your color change. If you get a color change right away, increase the amount of HCl so that you get a more gradual color change. If you add a whole burette of NaOH and get no color change, cut the HCl in half and dilute to the same volume and titrate. Repeat until you get a definite end point and then calculate based on your knowns.