21 Practice Problem 7-9Ibuprofen, C13H18O2, is the active ingredient in many nonprescription pain relievers. Its molar mass is g/mol.If the tablets in a bottle contain a total of 33 g. of ibuprofen, how many moles of ibuprofen are in the bottle?0.16 mol
22 9.6 x 1022 Molecules Practice Problem 7-9 Ibuprofen, C13H18O2, is the active ingredient in many nonprescription pain relievers. Its molar mass is g/mol.How many molecules of ibuprofen are in the bottle?9.6 x 1022 Molecules
23 Practice Problem 7-9Ibuprofen, C13H18O2, is the active ingredient in many nonprescription pain relievers. Its molar mass is g/mol.What is the total mass in grams of carbon in 33 g. of ibuprofen?25 g
24 7.4 Determining Chemical Formulas The simplest formula or empirical formula consists of the symbols for the elements combined with subscripts showing the smallest whole-number ratio of the atoms.
25 ExampleDiborane has a molecular formula and in reality exists as B2H6.The empirical formula is BH3.Both are 78% Boron and 22% Hydrogen.
26 Simplest Formula (from weight percents.) Step 1: Take percentages and convert to a total of 100 g.Diborane is 78% by weight Boron and 22% by weight hydrogen.100 g would be 78 g. of Boron and 22 g. of Hydrogen.
27 Simplest Formula (cont.) Step 2: Determine moles.
28 Simplest Formula (cont.) Step 3: Determine simplest whole number molar ratio.Divide through by the smallest number.
29 Simplest Formula (cont.) 7.1 mol of Boron; 22 mol H1.0 mol B : 3.1 mol HEmpirical formula is BH3
30 Practice ProblemAnalysis shows a compound to contain 26.56% potassium, 35.41% chromium, and % Oxygen by weight. Find the simplest formula for this compound.K2Cr2O7.
31 Molecular FormulaThe simplest or empirical formula may or may not the correct molecular formula.Is the correct (real) formula BH3, B2H6, B3H9 ?Need to know the molecular mass of the formula.
32 Molecular Formula (cont.) If the formula mass of the empirical formula equals the known molecular mass, then it is the molecular formula.
33 Molecular Formula (cont.) If not, there is a whole number multiplier, x, for all of the subscripts.
34 Empirical formula is BH3 The BH3 has a formula mass of u.The known formula mass for Diborane is u.