2 Law of Conservation of Mass The Law of Conservation of Mass indicates that in an ordinary chemical reaction,Matter cannot be created or destroyed.No change in total mass occurs in a reaction.Mass of products is equal to mass of reactants.
3 Conservation of Mass + Reactants Products 2 moles Ag moles S = mole Ag2S2 (107.9 g) (32.1 g) = (247.9 g)= g
4 Reading Equations with Moles Consider the following equation:4Fe(s) O2(g) Fe2O3(s)This equation can be read in “moles” by placing theword “moles” between each coefficient and formula.4 moles Fe moles O moles Fe2O3
5 Writing Mole-Mole Factors A mole-mole factor is a ratio of the moles for any two substances in an equation.4Fe(s) O2(g) Fe2O3(s)Fe and O moles Fe and 3 moles O23 moles O moles FeFe and Fe2O moles Fe and 2 moles Fe2O32 moles Fe2O3 4 moles FeO2 and Fe2O3 3 moles O and 2 moles Fe2O32 moles Fe2O3 3 moles O2
6 Learning Check Consider the following equation: 3 H2(g) N2(g) NH3(g)A. A mole-mole factor for H2 and N2 is1) 3 moles N ) 1 mole N ) 1 mole N21 mole H moles H moles H2B. A mole-mole factor for NH3 and H2 is1) 1 mole H ) 2 moles NH ) 3 moles N22 moles NH moles H moles NH3
7 Solution 3H2(g) + N2(g) 2NH3(g) A. A mole-mole factor for H2 and N2 is 2) 1 mole N23 moles H2B. A mole-mole factor for NH3 and H2 is2) 2 moles NH3
8 Calculations with Mole Factors How many moles of Fe2O3 can be produced from6.0 moles O2?4Fe(s) O2(g) Fe2O3(s)Relationship: 3 mole O2 = 2 mole Fe2O3Write a mole-mole factor to determine the moles of Fe2O3.6.0 mole O2 x 2 mole Fe2O3 = 4.0 moles Fe2O33 mole O2