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Ch.3 - Molecules and Compounds
Chapter 3, Problem 83a

Calculate mass (in grams) of sodium in 8.5 g of each sodium containing food additive. a. NaCl (table salt) b. Na3PO4 (sodium phosphate) c. NaC7H5O2 (sodium benzoate) d. Na2C6H6O7 (sodium hydrogen citrate)

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1
Step 1: Determine the molar mass of NaCl.
Step 2: Calculate the mass percentage of sodium (Na) in NaCl using the formula: \( \text{Mass percentage of Na} = \left( \frac{\text{Molar mass of Na}}{\text{Molar mass of NaCl}} \right) \times 100 \% \).
Step 3: Use the mass percentage of sodium to find the mass of sodium in 8.5 g of NaCl.
Step 4: Apply the formula: \( \text{Mass of Na} = \left( \frac{\text{Mass percentage of Na}}{100} \right) \times \text{Mass of NaCl} \).
Step 5: Calculate the mass of sodium in 8.5 g of NaCl using the values obtained in the previous steps.

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Key Concepts

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

Molar Mass

Molar mass is the mass of one mole of a substance, typically expressed in grams per mole (g/mol). For sodium chloride (NaCl), the molar mass is calculated by adding the atomic masses of sodium (Na) and chlorine (Cl), which are approximately 23 g/mol and 35.5 g/mol, respectively. This concept is essential for converting between grams and moles in stoichiometric calculations.
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Stoichiometry

Stoichiometry is the area of chemistry that deals with the relationships between the quantities of reactants and products in chemical reactions. It allows us to calculate the amount of a substance in a mixture based on its proportion to other components. In this case, stoichiometry helps determine the mass of sodium in a given mass of NaCl by using the ratio of sodium's molar mass to the total molar mass of NaCl.
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Mass Percentage

Mass percentage is a way of expressing the concentration of an element in a compound, calculated as the mass of the element divided by the total mass of the compound, multiplied by 100. For NaCl, the mass percentage of sodium can be found by dividing the molar mass of sodium by the molar mass of NaCl and then multiplying by 100. This concept is crucial for determining how much sodium is present in a specific mass of the additive.
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