Polly Esther determined the Ca2+ ion content of a 100 mL sample of calcium forti
ID: 785953 • Letter: P
Question
Polly Esther determined the Ca2+ ion content of a 100 mL sample of calcium fortified orange juice. After adding 2.0 M HCl solution to the sample, she filtered the juice to remove the pulp and other particulate matter. Then the student added sodium carbonate (Na2CO3) solution to precipitate calcium carbonate (CaCO3). She recovered 0.2818 g of calcium carbonate from the mixture. There were [ ] mg (1 dec place) of Ca2+ in the sample. The density of the juice was 0.958 g/mL, therefore the mass percent of Ca2+ ion in the juice sample was [ ] %. (3 dec places)Explanation / Answer
(0.2818 g of CaCO3) * (40.08 g of Ca^+2 ion mol / 100.1 g of CaCO3 mol) = 1.128 x 10^-1 g
in mg I would just * 1000 and get 112.8 mg
1.128 x 10^-1 g/ analyzed sample
then *'s 100 = mass percent
*0.958 is a mass of 1 mL, not of the analyzed sample
0.118%