ChemicalChemical RtiReactionsChapter 17Chapter 17click here for 9/page to printAtomic vs Molecular WeightAtomic vs. Molecular Weight• Atomic weight on periodic table is average of natural abundance of isotopesp• Atomic mass is the number of nucleons in a particular atomspecified by isotopea particular atom—specified by isotope• Molecular mass is the mass of one mole of molecules–One atomic mass number of gramsOne atomic mass number of grams– 6.0221367x1023moleculesCalculate Molecular MassCalculate Molecular Mass• O atomic weight 15.9996 (round to 16 for this class))• O-16 atomic mass 16 uMl lOti 32•Molecular oxygen O2atomic mass 32 u•Molecular O2molecular mass 32 g/moleoecuaO2o ecu a ass 3 g/ o eCO2molecular mass C=12 g/mole, O2=32 g/moleCO2=12+32=44 g/moleCO212+32 44 g/moleNaCOmolecular massNa2CO3molecular mass• Na = 23 g/mole•C=12 g/moleC 12 g/mole• O = 16 g/mole • 3 O, so multiply 16 x 3•23 + 12 + 48 = 83 g/mole•23 + 12 + 48 = 83 g/moleWrite these downWrite these down•C = 12•H=1H 1•O = 16• Use for the next questionWhat is the sum of the atomic masses of all the atoms in sucrose, C12H22O11?sucrose, C12H22O11?1. 182 amu2270 amu2.270 amu3. 342 amu4. none of the above0% 0%0%0%1234Grams calculated from MolesGrams calculated from Moles• Find the molar mass of substance Na=23moleg mole of Na 41mole• Multiply molar mass times moles• 23 x 0.250 moles = 5.75 gmoleggmoleMoles calculated from GramsMoles calculated from Grams• 176 g of CO2 = Number of moles?• Molar mass of CO2= 44 moleg2 • If you multiply, 176 g x 44 results in units oflgg2mole176 g x 44 results in units of you get a unit messUNITSalert you that you made an errormolemoleUNITSalert you that you made an error KEEP UNITS WITH NUMBERS!!Moles calculated from GramsMoles calculated from Grams• 176 g of CO2 = Number of moles?• Molar mass of CO2= 44 moleg2 • Divide 176 g by 44•Same as multiply by reciprocalmoleg•Same as multiply by reciprocal(1mole)176 g x (1 mole44 g)= 4 moles CO2• Now the grams cancel =)Mass to moles relationshipMass to moles relationshipTo convert between grams and molesTo convert between grams and moles• Make sure equation is balanced•So you know the molar ratios of themSo you know the molar ratios of them• Find molar mass of them• Set up proportions for moles and gramsProportionsProportions• Mathematical device to compare ratios• Cross-multiply to solve•Correctly organized•Correctly organized• Be sure you keep same:same in columns and rowsProportions to find grams and molesProportions to find grams and moles• Correctly organizedExample a of a of moles g=b of b of moles g=orb f b of moles f a of moles=•crossmultiply to solveb of a of gg•cross-multiply to solveProportionsProportions• Correctly organized•It doesn’t matter how you write the first ratioIt doesn t matter how you write the first ratio, as long as you label the numbersTt t k thtit•Try to put unknown on the top—easier to solve• The second ratio needs to match the firstProblemNOONO→+Problem22NOONO→+• 64 grams O2• How many grams NO2produced?yg2pFirst: Balance Equation22NOONO+2222NOONO→+Problem2222NOONO→+Problem2222NOONO→+• 64 grams O2• How many grams NO2produced?yg2pBalance EquationDetermine molar ratios of them 1:2Determine molar ratios of them 1:2Find molar mass of each component NO46 O32 (NO 30 )NO2=46 g, O2=32 g, (NO=30 g)Problem2222NOONO→+Problem2222NOONO→+• 64 grams O2• How many grams NO2produced?yg2pMolar mass of each: O2=32 g, NO2=46 g How many moles is 64 grams O2?How many moles is 64 grams O2?One moleProblem2222NOONO→+Problem2222NOONO→+• 64 grams O2• How many grams NO2produced?yg2p• Molar mass of each O2=32 g, NO2=46 gMolar ratios O2:NO2 is 1:2TwomoleofOTwo mole of O2So four moles of NO2 is producedHow many grams is that?4molx46g/mol=184 grams4 mol x 46 g/mol 184 gramsProblemProblemOHSOOSH+→+OHSOOSH2222+→+• 32 grams SO2•How many grams O2used?How many grams O2used?Problem• 32 grams SO2•How many grams Oused?ProblemOHSOOSH+→+•How many grams O2used?•Balance firstOHSOOSH2222+→+Balance firstOHSOOSH22222232+→+•Then determine molar ratiosOHSOOSH22222232+→+Then determine molar ratios•2 SO2 to 3 O2Problem• 32 grams SO2•How many grams Oused?ProblemOHSOOSH2232•How many grams O2used?OHSOOSH22222232+→+• Find molar masses SO2= 32 + 32 = 64 g/mol SO2 O2 = (2x1) +16 = 32 g/mol O2HO= (2x1) +16=18 g/mol HOH2O= (2x1) +16 =18 g/mol H2O H2S= (2x1) +32 = 34 g/mol H2S 2()g2Problem• 32 grams SO2•How many grams Oused?ob eOHSOOSH2232+→+•How many grams O2used?OHSOOSH22222232+→+•32 g SOneeds how many grams O?•32 g SO2needs how many grams O2?• How many moles is 32 g SO2?SO50 1SOg32molesmole=22SO 5.0g 64SO g 32moles=⋅Problem• 32 grams SO2•How many grams Oused?ProblemOHSOOSH2232+→+•How many grams O2used?OHSOOSH22222232+→+•How many moles Ois needed?•How many moles O2 is needed?•0.5 moles SO2in 2:3 ratio with O2• 0.75 moles O222SO5.0 1SO g 32 molesmole=⋅22g64gSet up• 32 grams SO2•How many grams Oused?Set up proportion•How many grams O2used?ith th k t (th O)with the unknown on top (the O2)[]O?[][][] Og ?2=[][]Problem 6COOC→+Problem 622COOC→+Is it balanced?Molar ratio 1:1:1 4 grams oxygenGrams carbon consumed?Grams carbon consumed? Grams carbon dioxide produced?Problem 6COOC→+Problem 622COOC→+Molar ratio 1:1:1 4 grams oxygen• 1 mole O2= 32 g22125.01 4 OmolesmoleOg=⋅2232ggProblem 6COOC→+Problem 622COOC→+Molar ratio 1:1:1 0.125 moles O2in 1:1 ratio0.125 moles C0 125 l CO0.125 moles CO2Problem 6COOC→+Problem 622COOC→+0.125 moles CGrams carbon consumed?CggCmoles51121250=⋅CgmoleCmoles5.1 1125.0=⋅225.544mole 125.0 COggCO =⋅221gmoleReaction SpeedReaction SpeedCollision of molecules required for it to occur•Increase concentrationIncrease concentration• Increase temperature• Catalyst can facilitate reactionChlorine catalystChlorine catalystEnergy of reactionsEnergy of reactions• Release energy•EXOTHERMICEXOTHERMIC• Methane combustion•Consume energy•Consume energy• ENDOTHERMIC• Formation of
View Full Document
Unlocking...