[Bakr99]

A 9.78 g sample of lead ore ,mostly composed of cerussite (lead  ii carbonate) was Analyse as follows the Sample was grounded to fine powder Then placed into 50 mL of 2.00 mole Per litre of nitric acid until no further action occurred The solution was boiled to drive off all the carbon dioxide then 20 mL we are titrated with standard 0.156 mole per litre sodium hydroxide solution an average of 35.76 mL of the standard Solution was required for a complete neutralisation calculate the percentage by mass of the lead in the Sample?
The answer is should be %90.4 can someone please tell me how to work it out I’ve been trying for hours thank you

[ACETAT]

From the titration you get the nitic acid what is left.
This you have to compare how much nitric was used. The difference gives the amount which react with the ore. The mole of this nitric correspond to how much mole Pb. Convert this to the mass. The rest is percentage calculation.
Beware the aliqout between.