The “Accounting” of Chemistry Thornburg 2014

 To better understand chemical reactions, we can compare a chemical equation to a recipe  A recipe tells us how much of each ingredient is needed to make a specific amount of the finished product Thornburg 2014

Example: making sandwiches recipe  To make one sandwich, use the following recipe: ○ 2 pieces of bread (B) ○ 2 slices of turkey (T) ○ 1 slice of cheese (C) ○ 3 pickles (P) ○ 1 packet of mayonnaise (M) Thornburg 2014

 Write down a “formula” for one sandwich: B 2 T 2 CP 3 M  We can write our recipe in the form of an equation: B + T + C + P + M B 2 T 2 CP 3 M  Balance this equation 2B + 2T + C + 3P + 1M 1B 2 T 2 CP 3 M Thornburg 2014

We can determine the following information from a balanced equation…  The amount of products produced relative to the amount of reactants used  We can measure these amounts using various quantities: ○ Moles ○ Grams ○ Number of atoms ○ Number of molecules ○ liters Thornburg 2014

`  Example #1: How many pickles are needed to make 24 sandwiches? Step 1 – determine your conversion factor from your balanced equation 1 sandwich or 3 pickles 3 pickles 1 sandwich Step 2 – find your unknown quantity by using dimensional analysis 24 sandwiches X 3 pickles = 72 pickles 1 sandwich Thornburg 2014

 Example #2: How many slices of turkey are needed to make 17 sandwiches? Step 1 – determine your conversion factor from your balanced equation 1 sandwich or 2 slices turkey 2 slices turkey 1 sandwich Step 2 – find your unknown quantity by using dimensional analysis 17 sandwiches X 2 slices turkey = 34 slices 1 sandwich turkey Thornburg 2014

Mass of “A” (Grams) Volume of “A” (Liters) Particles of “A” Particles of “B” Volume of “B” (Liters) Mass of “B” (Grams) Moles of “A” Moles of “B” The Complete Mole Road Map 1 mole 22.4 Liters 1 mole 6.02 x mole mole B Moles A Molar mass (g) 1 mole 22.4 Liters 1 mole Molar mass (g) Thornburg 2014