[cathy]

I am doing a planning experiment. About 1g of eggshell will be given.
You are required to design an experiment to deterimine the percentage by mass of calcium carbonate in the eggshell by titration method. and also suggest another experiment which can be carried out to determine the precentage by mass of calcium carbonate in eggshell.

On titration method side, I am planning to use 0.1M HCL to dissolve the CaCO₃ in the eggshell first,
filter the mixture, and then use NaOH to titrate with that filtrate, to find out the answer.

Am I correct?
could anyone suggest another experiment to determine the answer?
thx a lot > W <//

[AWK]

Yes, the method of back titration is the best in this case.

[Alberto_Kravina]

Or you could titrate the dissolved egg shell with EDTA...

[tonyliruhan]

maybe you can just heat it
CaCO3(s)----->CaO+CO2
but the temperature is a bit hard to reach
you will need some particular tools

[xiankai]

or u could dissolve the eggshell completely in the acid and measure the amount of CO2 produced.

[Borek]

Roasting can be a step in alaysis, but it doesn't give a quantitave answer.

Measuring CO₂ is either imprecise or requires additional glass, so will be not good idea.

That leaves back titration of acid and EDTA titration. I would go for the first, as AFAIR end point detection in complexometry is harder than in acid-base titrations. Although someone may argue that back titration has one error source more.

[cathy]

thx a lot ~~^ ^
Beside the back titration method,
Is measuring the volume of CO₂ given out is the best method of
calculate the percentage of CaCO₃ in the eggshell
THX THX

[Borek]

If you are going to measure CO₂ volume, precision will be catastrophical. If you are going to absorb it in some basic solution and titrate excess base, you better titrate excess acid left after shell dissolution. Less glass used, less possible procedural errors, less things to worry about.