Chemistry (mass)

Question

1. The daily recommended intake of calcium for adolescent females is approximately 1.10 g. 

 

b)  Each tablet of calcium citrate contains 4.57 X 10-3 mol calcium citrate. How many tablets would an adolescent female have to take to meet her requirements? [2]

Answer 1

If you look up calcium citrate, you'll see there are 3 Ca for each calcium citrate. There are also 2 citrates. So, the formula is Ca₃(citrate)₂ or Ca₃(C₆H₅O₇)₂

The molar mass of calcium citrate = 498 g/mol

The amount of Ca in 1 mol = 3 x 40 g = 120 g

% Ca = 120 g / 498 g (x100%) = 24.1 % calcium

Use dimensional analysis to find the number of tables needed for 1.10 g of Ca

4.57x10^-3 mol CaCitrate/tablet x 120 g Ca/mol CaCitrate = 0.548 g Ca per tablet

1.10 g Ca x 1 tablet / 0.548 g Ca = 2.00 tablets

If you wanted to use % composition, you could proceed as follows:

4.57x10-3 mol / tablet x 498 g / mol x 0.241 Ca = 0.548 g Ca per tablet

1.10 g Ca x 1 tablet /0.548 g Ca = 2.00 tablets