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The masses of Calcium Carbonate precipitate resulting from vacuum filtering varying concentrations of Calcium Hypochlorite solution are graphed below. The masses were found to be 0.3, 0.72, and 1.93 grams at 10 g/L, 20 g/L, and 30 g/L, respectively. The mass of precipitate was found to increase with increasing concentration of solution. From these resulting masses and the known molecular weights of Calcium Hypochlorite going in, the amount of Calcium Carbonate that could precipitate out was calculated. And based on the amount of Calcium Carbonate we found that actually did precipitate out of solution, we were able to find the residual mass of Calcium left in solution that could potentially settle out at a later time and clog the hypochlorinators.
Using the reaction below (Reaction 1), we could see that for For every mole of calcium hypochlorite (Ca(ClO)2) one mole of calcium carbonate (CaCO3) precipitates out in solution.
Reaction 1: Calcium Hypochlorite Reacting in Solution to form Calcium Carbonate
2Ca(ClO)2 + 2CO2 → 2CaCO3 + 2Cl2 + O2
Using Using this and the fact that the molecular weight of calcium hypochlorite is 142.98 g/mol and the known masses of calcium hypochlorite added were 10, 20, and 30 g, the moles of calcium added were found to be 0.7, 0.14, and 0.21, respectively. Therefore the mass of calcium (molecular weight: 40.08 g/mol) going into solution was found to be 2.8, 5.6, and 8.4 g, respectively. Then using the molecular weight of calcium carbonate (100.09 g/mol) and the known masses of calcium carbonate coming out of solution (0.3, 0.72, and 1.93 at 10 g/L, 20 g/L, and 30 g/L, respectively as mentioned above), the moles of calcium carbonate and thus calcium coming out were found to be 0.003, 0.007, and 0.019, respectively. From this the mass of calcium coming out of solution was found to be 0.12, 0.29, and 0.77 g respectively. By subtracting the amount of calcium coming out of solution from the amount of calcium going into solution, the residual mass at each concentration was found.
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