[Borek]

Depens on whether you have access to balance or not. Question dosn't state anything about glass nor devices that can be used, so it not clear what you can and what you can't.

Can we just weigh the sample of Al₂O₃ and Fe at first ,without adding any reagents,using a chemical balance?
So then we would have the mass percent of Al=(mass of Al/total mass of initial sample)*100 percent,

Plese elaborate - how do you want to determine amount of impurities knowing only mass of the sample.

[leena]

I'm sorry I don't understand.why do I need to find the amount of impurities?
We're only asked to find the mass percent of Al in the original sample,right?

[Borek]

By impurities I mean iron.

Do you mean you just want to weight the original sample, then determine amount of Al₂O₃? That will work, although it seems to me it is easier to dissolve sample in NaOH, filter iron and weight it after drying. Could be difficult to not let it oxidize.

[leena]

Plese elaborate - how do you want to determine amount of impurities knowing only mass of the sample.

By impurities I mean iron.

very sorry.I thought you meant tofind other impurities as well,cause the question doesn't state that Fe is the only impurity present.Sorry I misunderstood.

Thank you all for the help

[leena]

Sorry to bother you,but I just want to clarify.
Al₂O₃ + NaOH  NaAlO₂ + H₂O
If we add HCl dropwise to this solution ,the white ppt of Al₂O₃ can be reobtained from the clear NaAlO2 solution,right?
So can't we just filter this precipitate ,dry and weigh it?

If we add HCl dropwise to this solution ,the white ppt of Al₂O₃ can be reobtained from the clear NaAlO2 solution,right?

If this were true,wouldn't this affect the titration method we've used here?

Thank you.