Percentage Composition Chapter 6.1 Percentage Composition

Percent Composition Percent composition is the percentage of each element in a compound (by mass) Percent composition can be determined from either: the formula of the compound the experimental mass analysis of the compound Note: The percentages may not always total to 100% due to rounding 12

Combustion Analysis

Percent Composition Calculations To determine Percent Composition from the chemical formula: Determine the molar mass of compound Multiply the molar mass of the element of interest by the number of atoms per molecule then Divide this value by the molar mass of the compound

Percent Composition Calculations Example: The percent composition of sodium in table salt. The molar mass of NaCl is 58.44 g/mol There is 1 atom of Na in each NaCl formula unit The molar mass of Na is 22.99 g/mol

EXAMPLE: What is the percent composition of chloroform, CHCl3, a substance once used as an anesthetic? MCHCl3 = 1(M)C + 1(M)H + 3(M)Cl = (12.01 + 1.01 + 3 × 35.45)g/mol = 119.37g/mol

EXAMPLE: What is the percent composition of chloroform, CHCl3, a substance once used as an anesthetic? MCHCl3 = 1(M)C + 1(M)H + 3(M)Cl = (12.011 + 1.00797 + 3 × 35.453)g = 119.377g 1(M) %C = ------------ × 100 MCHCl3

EXAMPLE: What is the percent composition of chloroform, CHCl3, a substance once used as an anesthetic? MCHCl3 = 1(M)C + 1(M)H + 3(M)Cl = (12.011 + 1.01 + 3 × 35.45)g = 119.37g 1(M) %C = ------------ × 100% MCHCl3 1(12.01) %C = -------------- × 100% = 10.061% C 119.37

EXAMPLE: What is the percent composition of chloroform, CHCl3, a substance once used as an anesthetic? MCHCl3 = 1(M)C + 1(M)H + 3(M)Cl = (12.01 + 1.01 + 3 × 35.45)g = 119.37g 1(1.01) %H = -------------- × 100% = 0.846109% H 119.37 = 0.85 % H

EXAMPLE: What is the percent composition of chloroform, CHCl3, a substance once used as an anesthetic? MCHCl3 = 1(M)C + 1(M)H + 3(M)Cl = (12.01 + 1.01 + 3 × 35.45)g = 119.37g 3(35.45) %Cl = -------------- × 100% = 89.09% Cl 119.37

EXAMPLE: What is the percent composition of chloroform, CHCl3, a substance once used as an anesthetic? MCHCl3 = 1(M)C + 1(M)H + 3(M)Cl = 119.37g %C = 10.061% C = 10.06% C %H = 0.846109% H = 0.85% H %Cl = 89.093% Cl = 89.09% Cl 100.00% total

Percent Composition Calculations Perform the following % Composition calculations: The % composition of carbon in carbon monoxide The % composition of oxygen in water The % composition of chlorine in sodium hypochlorite (NaClO)

One Mole of each Substance Clockwise from top left: 1-Octanol, C8H17OH; Mercury(II) iodide, HgI2; Methanol, CH3OH; and Sulfur, S8.