#### Percent Composition

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Vitamin C, also known as ascorbic acid, is water soluble and cannot be produced by the human body. Each day, a person’s diet should include a source of vitamin C, such as orange juice. Ascorbic acid has a molecular formula of C6H8O6 and a gram-formula mass of 176 grams per mole.

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Baking soda, NaHCO3, can be commercially produced during a series of chemical reactions called the Solvay process. In this process, NH3(aq), NaCl(aq), and other chemicals are used to produce NaHCO3(s) and NH4Cl(aq).

To reduce production costs, NH3(aq) is recovered from NH4Cl(aq) through a different series of reactions. This series of reactions can be summarized by the overall reaction represented by the unbalanced equation below.

NH4Cl(aq) + CaO(s) → NH3(aq) + H2O(ℓ) + CaCl2(aq)

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A sample of calcium carbonate, CaCO3, has a mass of 42.2 grams. Calcium carbonate has a gram-formula mass of 100. g/mol.

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Given the unbalanced equation showing the reactants and product of a reaction occurring at 298 K and 100. kPa:

P4(s) + Cl2(g) → PCl3(ℓ) + energy

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John Dalton, an early scientist, sketched the structure of compounds using his own symbols for the elements known at the time. Dalton’s symbols for four elements and his drawing of potassium aluminum sulfate are represented by the diagram below.

Today, it is known that the chemical formula for potassium aluminum sulfate is KAl(SO4)2\u202212H2O. It is a hydrated compound because water molecules are included within its crystal structure. There are 12 moles of H2O for every 1 mole of KAl(SO4)2. The compound contains two different positive ions. The gram-formula mass of KAl(SO4)2\u202212H2O is 474 grams per mole.

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Some compounds of silver are listed with their chemical formulas in the table below.

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The two naturally occurring isotopes of antimony are Sb-121 and Sb-123. The table below shows the atomic mass and percent natural abundance for these isotopes.

Antimony and sulfur are both found in the mineral stibnite, Sb2S3. To obtain antimony, stibnite is roasted (heated in air), producing oxides of antimony and sulfur. The unbalanced equation below represents one of the reactions that occurs during the roasting.

Sb2S3(s) + O2(g) → Sb2O3(s) + SO2(g)

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