[portugal]

A 25.0ml aliquot of a solution containing sodium carbonate and sodium hydrogen carbonate was titrated with 0.0800M HCl(aq). A volume of 27.50mL of 0.800M HCl(aq) was needed to reach phenolphtalein endpoint. on addition of screened methyl orange, a further 32.50mL of the acid were needed to turn this indicator to its natural colour. find the concentrations as molarities of soidu carbonate and sodium hydrogen carbonate in orginal solution??

have a go at this its getten me pscyched up coz i cant jump at it like i usually do wid first year uni chem

[Borek]

Why do you use two different indicators?

[portugal]

its for both endpoints as Na2CO3 is done first then NaHCO3

[Borek]

OK

Hint: you have two unknowns and you can set up of system of equations. Of these one will be with one unknown, which makes calculations much simpler.

[portugal]

i cant seem to get does someone want post an answer

[AWK]

its for both endpoints as Na2CO3 is done first then NaHCO3

At the first enpoint you titrate half of Na2CO3,  at the second enpoint - the rest