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April 25, 2014

Homework Help: college chemistry

Posted by anne on Monday, October 8, 2012 at 9:37pm.

a student determined the Ca^2+ ion content of a 100mL sample of calcium-fortified orange juice. After adding 2.0M HCl solution to the sample, the student filtered the juice to remove the pulp and other particulate matter. Then the tudent added Na2CO3 solution to precipitate CaCO3. The student recovered 0.2818g of CaCO3 from the resulting mixture.

a)why is it important for the student to add HCl before filtering the juice to remove pulp?
i said because if you were to dissolve it with water, the calcium would ppt out as Ca(OH)2 so instead we use HCl so that the Ca forms CaCl2 and stays in solution. is that true?

b)according to the juice label, "each serving contains 20% of the USRDA of calcium," and one serving is defined as 6 oz or 178mL. Does the student's analysis verify this claim? Briefly Explain.


Please be specific and I'd appreciate any help I could get! thanks!

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