Percent Composition of Compounds PDF

Percent means parts per 100 parts. Just as each piece of pie is a percent of the whole pie, each element in a compound is a percent of the whole compound. The percent composition of a compound is the mass percent of each element in the compound. The molar mass represents the total mass, or 100%, o...

Percent means parts per 100 parts. Just as each piece of pie is a percent of the whole pie, each element in a compound is a percent of the whole compound. The percent composition of a compound is the mass percent of each element in the compound. The molar mass represents the total mass, or 100%, of the compound. The percent composition of a compound can be determined (1) from knowing its formula or (2) from experimental data Percent Composition from Formula - If the formula of a compound is known, a two-step process is needed to determine the percent composition: Problem-Solving Strategy for Calculating Percent Composition from Formula 1.Calculate the molar mass. 2. Divide the total mass of each element in the formula by the molar mass and multiply by 100. This gives the percent composition: Example # 1: Calculate the percent composition of sodium chloride (NaCl). Given: NaCl Unknown: % composition of NaCl Calculate 1. We need to use the atomic masses of each element to find the molar mass of NaCl. Na = 22.99 g Cl = 35.45 g 58.44 g molar mass of NaCl 2. Calculate the percent composition for each element Example # 2: Calculate the percent composition of potassium sulfate (K2SO4). 2 atoms of Potassium Given: 1 atom of Sulfur 4 atoms of Oxygen Unknown: % composition of K2SO4 Calculate 1. We need to use the atomic masses of each element to find the molar mass of K2SO4. K = 2 (39.10) g = 78. 2 g S = 1 (32.07) g = 32.07 g O = 4 (16.00) g = 64 g 174.3 g molar mass of K2SO4. 2. Calculate the percent composition for each element Percent Composition from Experimental Data Problem-Solving Strategy for Percent Composition from Experimental Data 1.Calculate the mass of the compound formed. 2.Divide the mass of each element by the total mass of the compound and multiply by 100. Example : Zinc oxide is a compound with many uses from preventing sunburn to a pigment in white paint. When heated in air, 1.63 g of zinc (Zn) combines with 0.40 g of oxygen (O2) to form zinc oxide. Calculate the percent composition of the compound formed. Given: 1.63 g Zn 0.40 g O2 % composition of the Unknown: compound formed Calculate 1. We need to calculate the mass of the product formed. 1.63 g Zn 0.40 g O2 2.03 g product 2. Calculate the percent composition for each element. 80.30% 19.70% 100%