Mole Calculations - Enfield High School

Mole Calculations - Enfield High School

Visualizing a Chemical Reaction 2 Na 10 mole Na ___ + Cl 2 5 mole Cl2 ___ 2 NaCl 10 ? mole NaCl ___ Formation of Ammonia Proportional Relationships 2 1/4 c. flour 1 tsp. baking soda 1 tsp. salt Conversion Factor

1 c. butter 3/4 c. sugar 3/4 c. brown sugar 1 tsp vanilla extract 2 eggs 2 c. chocolate chips Makes 5 dozen cookies. I have 5 eggs. How many cookies can I make? 5 eggs 5 dozen 2 eggs Ratio of eggs to cookies 150 dozen cookiescookies = 12.5 Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem Proportional Relationships Stoichiometry mass relationships between substances in a chemical reaction based on the mole ratio

Mole Ratio indicated by coefficients in a balanced equation 2 Mg + O2 2 MgO Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem Stoichiometry Steps 1. Write a balanced equation. 2. Identify known & unknown. 3. Line up conversion factors. Mole ratio Molarratio mass Mole - Molarity Molar volume - moles moles moles grams moles

moles moles liters soln moles liters gas Core step in all stoichiometry problems!! 4. Check answer. Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem Molar Volume at STP 1 mol of a gas=22.4 L at STP Standard Temperature & Pressure 0C and 1 atm Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem Molar Volume at STP LITERS OF GAS AT STP Molar Volume (22.4 L/mol) MASS IN GRAMS

Molar Mass (g/mol) 6.02 1023 MOLES particles/mol NUMBER OF PARTICLES Molarity (mol/L) LITERS OF SOLUTION Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem Stoichiometry Problems How many moles of KClO3 must decompose in order to produce 9 moles of oxygen gas? 2KClO3 2KCl + 3O2 ? mol

9 mol O2 2 mol KClO3 3 mol O2 9 mol = 6 mol KClO3 Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem 1. 2 Sb + 3 Cl2 2 SbCl3 2. 2 Mg + O2 2 MgO 3. CaCl2 Ca + Cl2 4. 2 NaClO3 2 NaCl + 3 O2 5. Fe + 2 HCl FeCl2 + H2 6. CuO + H2 Cu + H2O 7. 2 Al + 3 H2SO4 Al2(SO4)3 + 3 H2 2 5 mol 1. 2 Sb + 3 Cl2 2 SbCl3 excess 5 mol

7.5 excess x mol mol = 3 x mol 2 x = 15 x = 7. 5 mol x mol How many moles of chlorine gas are required to react with 5 moles of antimony? x mol Cl2 = 5 mol Sb 3 mol Cl2 2 mol Sb = 7.5 mol Cl2 How many moles of SbCl3 are produced from 5 moles of antimony and excess Cl2? x mol SbCl3 = 5 mol Sb

2 mol SbCl3 2 mol Sb = 5 mol SbCl3 How many moles of SbCl3 are produced from 7.5 moles of Cl2 and excess Sb? x mol SbCl3 = 7.5 mol Cl2 2 mol SbCl3 3 mol Cl2 = 5 mol SbCl3 2. 2 Mg + O2 2 MgO 10 mol xL x mol How many moles of magnesium oxide are produced from the burning of 10 mol of Mg? x mol MgO = 10 mol Mg 2 mol MgO 2 mol Mg

= 10 mol MgO How many liters of oxygen are needed to burn 10 mol of Mg? Assume 1 mol O2 = 22.4 L x L O2 = 10 mol Mg x L O2 = 10 mol Mg 1 mol O2 2 mol Mg = 5 mol O2 1 mol O2 22.4 L O2 2 mol Mg 1 mol O2 22.4 L O2 1 mol O2 = 112 L O2 = 112 L O2

3. CaCl2 Ca + Cl2 8 mol x mol How many moles of calcium metal and chlorine gas are produced from the decomposition of 8 mol of calcium chloride? x mol Ca = 8 mol CaCl2 1 mol Ca 1 mol CaCl2 = 8 mol Ca How many moles of calcium metal and chlorine gas are produced from the decomposition of 8 mol of calcium chloride? x mol Cl2 = 8 mol CaCl2 1 mol Cl2 1 mol CaCl2 = 8 mol Cl2 Ions in Aqueous Solution Pb(NO3)2(s) + H2O(l) Print

Print Copy Copy ofofLab Lab Pb(NO3)2(aq) Pb2+(aq) + 2 NO31(aq) Pb2+ NO31 NO31 dissociation: NaI(s) + H2O(l) Na1+ I1 add water NO31 Pb2+ NO31 NaI(aq)

Na1+(aq) + I1(aq) Na1+ I1 Mix them and get Balance to get overall ionic equation Cancel spectator ions to get net ionic equation in solution Solubility Chart Mix them and get Pb(NO3)2(aq) + 2 NaI(aq) Pb2+ Na1+ (aq) + 2 Na1+(aq) PbI22(s) (s) ++ 2NaNO NO313 (aq) I1

NO31 Pb2+ NO31 I1 Na1+ solid I1 NO31 in solution Na1+ I1 Na1+ NO31 Balance to get overall ionic equation

Pb2+(aq) + 2 NO31(aq) + 2 Na1+(aq) + 2 I1(aq) PbI2(s) + 2 NO31(aq) + 2 Na1+(aq) Cancel spectator ions to get net ionic equation Pb2+(aq) + 2 I1(aq) PbI2(s) Solubility Chart Mix together Zn(NO3)2(aq) and Ba(OH)2(aq): Mix them and get Ba(NO3)2 (aq) and Zn(NO3)2(aq) + Ba(OH)2(aq) Zn(OH)2 (ppt) Zn(OH)2(s) + 2 NO31(aq) + Ba2+(aq) Zn(NO3)2(aq) Ba(OH)2(aq) Zn2+(aq) + 2 NO31(aq)

Ba2+(aq) + 2 OH1(aq) OH1 NO31 Ba2+ Zn2+ NO31 OH1 Balance to get overall ionic equation Zn2+(aq) + 2 NO31(aq) + Ba2+(aq) + 2OH1(aq) Zn(OH)2(s) + 2 NO31(aq) + Ba2+(aq) Cancel spectator ions to get net ionic equation Zn2+(aq) + 2 OH1(aq) Zn(OH)2(s) 2 (NH4)3PO4 +3 Mg(OH)2 Mg3(PO4)2 ammonium phosphate

6 NH? 4OH + ammonium hydroxide magnesium phosphate magnesium hydroxide NH41+ Now you try 2 AlCl3 + 3 Li2CO3 Al2(CO3)3 + 6LiCl

OH1- Identify the spectator ions and write a net ionic equation when an aqueous solution of aluminum sulfate is mixed with aqueous ammonium hydroxide. Al3+ SO42- NH41+ OH1- Al3+ OH1- aluminum sulfate + ammonium hydroxide aluminum hydroxide + NH41+ SO42- ammonium sulfate Al2(SO4)3(aq) + 6 NH4OH(aq) 2 Al(OH)3 (ppt) + 3 (NH4)2SO4 (aq) 2 Al3+(aq) + 3 SO42-(aq) + 6 NH41+(aq) + 6 OH1-(aq) 2 Al(OH)3(ppt) + 6 NH41+(aq) + 3 SO42-(aq) spectator ions

2 Al3+(aq) + 6 OH1-(aq) 2 Al(OH)3(ppt) Net Ionic Equation Meaning of Coefficients 2 atoms Na 1 molecule Cl2 2 molecules NaCl 2 Na + Cl2 2 g sodium + 1 g chlorine 2 mol sodium (2 mol Na) x (23 g/mol) 2 NaCl = 1 mol chlorine (1 mol Cl2) x (71 g/mol) 46 g 71 g 117 g 2 g sodium chloride 2 mol sodium chloride

(2 mol NaCl) x (58.5 g/mol) 117 g Classes of Reactions Chemical reactions Precipitation reactions Oxidation-Reduction Reactions Combustion Reactions Acid-Base Reactions Summary of Classes of Reactions Chemical reactions Precipitation reactions Oxidation-Reduction Reactions

Combustion Reactions Synthesis reactions (Reactants are elements.) Acid-Base Reactions Decomposition reactions (Products are elements.) Summary of Classes of Reactions Chemical reactions Precipitation reactions Oxidation-Reduction Reactions Combustion

Reactions Synthesis reactions Acid-Base Reactions Decomposition reactions IONIC BONDING: Formation of Magnesium Chloride Cl Mg Cl Mg2+ Cl Loses 2e- Each gains 1eMg2+ Cl One magnesium ion Cl1[(2+)

MgCl2 Two chloride ions 2 (1-) = 0] magnesium chloride IONIC BONDING: Formation of Magnesium Chloride Cl Mg2+ Cl Mg2+ Cl Loses 2e- Each gains 1eMg2+ Cl One magnesium ion Cl1[(2+)

MgCl2 Two chloride ions 2 (1-) = 0] magnesium chloride

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