Question

help, i'd like to know how to do this titration question:

for example: a 1g sample of naoh contaminated with na2co3 is titrated with 0.500MHCl, and it is found that 46.5mL of HCl are required for neutralization. Find the percentage by mass Na2Co3.

( i did not make up these numbers, these numbers come right from the text book)

Answer 1

Alex--Is there any/some indication of the end point to which the NaOH/Na2CO3 was titrated? My point is that Na2CO3 to the phenolphthalein end point (about pH 9) titrates to NaHCO3 whereas Na2CO3 titrated to the methyl red or methyl orange end point (about pH 4 or 5) titrates to H2O and CO2, that is, two hydrogens are added to the Na2CO3. It makes a difference because in one case the HCl to Na2CO3 is 1:1 (same as NaOH and HCl) but in the other case (with both H added) the ratio is 2 HCl:1 Na2CO3. If there is some indication of that I can set up the problem for you to solve it. BUT, please post under a new question and include the information I need. I may not be thinking correctly but I think it can't be done unless we know to which end point it is titrated. My guess is to the phenolphthalein; generally; NaOH solutions contaminated with CO2 from the air (to make Na2CO3) does not introduce a titration error if we run to the MR or MO end points.