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Ch.6 Chemical Reactions: Mole and Mass Relationships
McMurry - Fundamentals of GOB 8th Edition
McMurry8th EditionFundamentals of GOBISBN: 9780134015187Not the one you use?Change textbook
Chapter 6, Problem 70b

Calcium citrate, Ca(C6H5O7)2(MW = 498.5 amu), is a common dietary supplement to provide calcium needed for strong teeth and bones.
b. What mass of calcium citrate would be needed to provide the recommended daily intake of calcium?

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1
Determine the molar mass of calcium citrate, which is given as 498.5 amu. This represents the mass of one mole of calcium citrate.
Identify the number of calcium atoms in one formula unit of calcium citrate. The formula Ca(C6H5O7)2 indicates there is 1 calcium atom per formula unit.
Calculate the molar mass of calcium (Ca) using the periodic table. The atomic mass of calcium is approximately 40.08 g/mol.
Determine the mass fraction of calcium in calcium citrate by dividing the molar mass of calcium by the molar mass of calcium citrate: \( \text{Mass fraction of calcium} = \frac{40.08}{498.5} \).
To find the mass of calcium citrate needed to provide the recommended daily intake of calcium, divide the recommended daily intake of calcium (in grams) by the mass fraction of calcium calculated in the previous step: \( \text{Mass of calcium citrate} = \frac{\text{Recommended daily intake of calcium}}{\text{Mass fraction of calcium}} \).

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Molar Mass Calculation

Molar mass is the mass of one mole of a substance, expressed in grams per mole (g/mol). For calcium citrate, the molar mass is calculated by summing the atomic masses of all atoms in its formula, Ca(C6H5O7)2. This value is essential for converting between grams of the compound and moles, which is necessary for determining how much calcium citrate is needed to meet dietary requirements.
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Calcium Daily Intake

The recommended daily intake of calcium varies by age and gender, but for most adults, it is around 1000 mg (1 g) per day. Understanding this requirement is crucial for calculating how much calcium citrate must be consumed to meet this intake, as the amount of elemental calcium in calcium citrate must be determined to ensure adequate supplementation.
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Elemental Calcium Content

Calcium citrate contains a specific percentage of elemental calcium, which is the actual calcium available for absorption in the body. To find out how much calcium citrate is needed to meet the daily intake, one must first determine the amount of elemental calcium in a given mass of calcium citrate. This involves using the molar mass of calcium and the molar mass of calcium citrate to calculate the proportion of calcium in the compound.
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