A student determined the Ca^2+ ion content in a sample of nonfat dry milk. For c

Question

A student determined the Ca^2+ ion content in a sample of nonfat dry milk. For complete titration of the Ca^2+ ion present, a sample weighing 1.483 g required 41.33 mL of 1 183 times 10^-2 M EDTA solution. Calculate the mass of Ca^2+ ion in the titrated sample. A 25.6-oz box of the powdered milk analyzed in (1) costs $5.46. Calculate the cost of 1 00 g of Ca^2+ ion as provided by this brand of dry milk. The label on a particular brand of instant pudding mix boasts that "a serving of this pudding provides a good source of dietary calcium. "According to the directions on the box, when prepared with 2 cups of milk, the package makes 4 servings, each providing 15% of the recommended daily allowance (RDA) of Ca^2+ ion. The RDA of Ca^2+ ion is 1.000 g. If the pudding were prepared by mixing it with water and 45.60 g of the milk powder described in (1) and (2), how many grams of Ca^2+ ion would actually be provided by the pudding mix itself? Many individuals increase their Ca^2+ ion intake by taking high-potency calcium tablets. A bottle of 60 tables, each containing 1.500 g of calcium carbonate (CaCO_3), costs $3.98. Calculate the number of grams of Ca^2+ ion present in one calcium tablet. How many cups of milk, each prepared by dissolving 22.7 g of the milk powder in Question 1, must a person drink to get the same amount of Ca^2+ ion present in one high-potency calcium tablet? Compare the cost of 1.00 g of Ca^2+ ion obtained from the milk powder to the cost of the same amount obtained from the calcium tablets.

Explanation / Answer

1. (1) moles of Ca2+ present = 1.183 x 10^-2 M x 41.33 ml = 0.50 mmol

mass of Ca2+ present = 0.50 x 40.08 g/mol/1000 = 0.0196 g

(2) 25.6 Oz powdered milk cost = $5.46

1 Oz = 28.35 g

1.483 g milk has 0.0196 g Ca2+

So, 1 g Ca2+ is in = 75.66 g milk = 2.67 Oz

cost for 1 g Ca2+ = 2.67 Oz x $5.46 = $14.58

(3) RDA = 1 g

45.60 g milk would have = 45.60 x 0.0196/1.483 = 0.603 g Ca2+

2. Calcium tablet

(1) grams of Ca2+ in each tablet = 1.5 x 40.08/100.1 = 0.60 g

(2) cups of drink required = 45.60/22.7 = 2 cups

(3) cost of 1 g Ca2+ from tablet = 2.5 g x 3.98/1.5 = $6.63

Cost of Ca2+ suplement from tablet is much lower than taking milk powder.

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