Calcium is 40% of the molar mass of caco3. How many liters of home water must be consumed daily to meet 1000mg of elemental calcium? The answer i come up with just doesn't seem right.
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That depends on what the concentration of calcium in the water is; without knowing that, it's impossible to say. Hard water contains a lot of CaCO3, where as "soft" water doesn't contain nearly as much. Either way, you'd have to drink a lot of water to get your daily amount of calcium. Let's say your water contains 200 ppm CaCO3, which is very hard water. One ppm (part per million) is equivalent to 1 mg/L, so 200 ppm = 200 mg/L of CaCO3. This is equal to 0.0002 mol/L of CaCO3.
Because 1000 mg of calcium is 0.025 mol of Ca, you'd need about 125 L of water to fulfill your daily allotment of calcium.
This is just an example calculation, of course; if the water is softer, you'll need a lot more than 125 L. The point is that even in hard water, the actual amount of calcium present is really quite small. This is why you need to get calcium from sources other than water, like dairy products.
Because 1000 mg of calcium is 0.025 mol of Ca, you'd need about 125 L of water to fulfill your daily allotment of calcium.
This is just an example calculation, of course; if the water is softer, you'll need a lot more than 125 L. The point is that even in hard water, the actual amount of calcium present is really quite small. This is why you need to get calcium from sources other than water, like dairy products.