REACTION STOICHIOMETRY 1792 JEREMIAS RICHTER The amount of substances produced or consumed in chemical reactions can be quantified 4F-1 (of 14)

INFORMATION FROM CHEMICAL EQUATIONS 2H 2 + O 2 → 2H 2 O 2 molecules 2 moles 0.84 moles moles 1 molecule 1 moles 0.42 moles moles 2 molecules 2 moles 0.84 moles moles 4F-2 (of 14) The moles that react and form do so in the ratio of the balanced equation

INFORMATION FROM CHEMICAL EQUATIONS 2H 2 + O 2 → 2H 2 O 0.60 moles moles 0.00 moles 0.40 moles moles 0.10 moles 0.00 moles moles 0.60 moles 4F-3 (of 14) starting reacting ending 0.50 moles moles 0.10 moles 0.20 moles moles 0.00 moles moles 0.40 moles starting reacting ending 2H 2 + O 2 → 2H 2 O The moles that react and form do so in the ratio of the balanced equation

MASS CALCULATIONS Calculate the mass of oxygen needed to burn 5.00 g of propanol, C 3 H 8 O. C 3 H 8 O + O 2 →CO 2 + H 2 O 34 4½ 4F-4 (of 14)

MASS CALCULATIONS Calculate the mass of oxygen needed to burn 5.00 g of propanol, C 3 H 8 O. C 3 H 8 O + O 2 →CO 2 + H 2 O g x g 2 mol9 mol mol C 3 H 8 O = 9 mol O g C 3 H 8 O x 9 mol O 2 _________________ 2 mol C 3 H 8 O = 12.0 g O 2 x 1 mol C 3 H 8 O ____________________ g C 3 H 8 O x g O 2 ______________ 1 mol O 2 4F-5 (of 14)

Calculate the mass of carbon dioxide produced from the 5.00 g of propanol. C 3 H 8 O + O 2 →CO 2 + H 2 O gx g 2 mol6 mol mol C 3 H 8 O = 6 mol CO g C 3 H 8 O x 6 mol CO 2 _________________ 2 mol C 3 H 8 O = 11.0 g CO 2 x 1 mol C 3 H 8 O ____________________ g C 3 H 8 O x g CO 2 ________________ 1 mol CO 2 4F-6 (of 14)

C 3 H 8 O + O 2 →CO 2 + H 2 O g6.0 g g11.0 g 4F-7 (of 14)

LIMITING REACTANT CALCULATIONS LIMITING REACTANT – The reactant that is completely used up in a reaction 4F-8 (of 14)

x 12 piecesx 1 sandwich _______________ 1 piece = 12 sandwiches 22 slicesx 1 sandwich _______________ 2 slices = 11 sandwichesactual amount produced limiting reactant 12 pieces22 slices 4F-9 (of 14)

Calculate the mass of tungsten metal produced when 25.0 g of barium reacts with 26.0 g of tungsten (III) fluoride. Ba + WF 3 →BaF 2 + W 25.0 g 26.0 g 3 mol 2 mol 323 x g 2 mol 2 4F-10 (of 14)

25.0 g Ba x 2 mol W ____________ 3 mol Ba = 22.3 g W x 1 mol Ba _______________ g Ba x g W ______________ 1 mol W Ba + WF 3 → 25.0 g 26.0 g 3 mol 2 mol 23BaF 2 + W3 x g 2 mol 2 Calculate the mass of tungsten metal produced when 25.0 g of barium reacts with 26.0 g of tungsten (III) fluoride. 4F-11 (of 14)

25.0 g Ba x 2 mol W ____________ 3 mol Ba = 22.3 g W x 1 mol Ba _______________ g Ba x g W _______________ 1 mol W Ba + WF 3 → 25.0 g 26.0 g 3 mol 2 mol 23BaF 2 + W3 x g 2 mol 2 Calculate the mass of tungsten metal produced when 25.0 g of barium reacts with 26.0 g of tungsten (III) fluoride g WF 3 x 2 mol W _____________ 2 mol WF 3 = 19.8 g W x 1 mol WF 3 _________________ g WF 3 x g W _______________ 1 mol W WF 3 is the limiting reactant 19.8 g W are produced 4F-12 (of 14)

Determine the percentage of magnesium and silver in an alloy of the two metals. A 6.50 gram sample of the alloy reacts with 14.5 grams of hydrogen chloride. Mg + HCl →MgCl 2 + H 2 x g14.5 g 1 mol2 mol 2 1 mol Mg = 2 mol HCl 14.5 g HCl x 1 mol Mg ______________ 2 mol HCl = g Mg x 1 mol HCl ________________ g HCl x g Mg ______________ 1 mol Mg 4F-13 (of 14) g Mg x 100 _______________ 6.50 g alloy = 74.4% Mg100% % = 25.6% Ag

A 1.17 gram sample of the unknown is dissolved in water, treated with lead (II) ions, and 1.42 grams of precipitate are collected. Pb 2+ + I - →PbI 2 x g 2 mol g 1 mol 1.42 g PbI 2 x 2 mol I - _____________ 1 mol PbI 2 = g I - x 1 mol PbI 2 _________________ g PbI 2 x g I - _____________ 1 mol I g I - ___________________ 1.17 g sample = 66.8% I - in the sample x 100 4F-14 (of 14) Determine the percentage by mass of iodide in a solid unknown.

MOLES FROM SOLUTION DATA Find the moles of potassium carbonate contained in 275 mL of a M potassium carbonate solution. M = n ___ V MV= n x L solution = mol K 2 CO mol K 2 CO 3 ______________________ L solution 4G-1 (of 12)

Find the moles of each ion in the M potassium carbonate solution mol K 2 CO 3 = mol K + x mol K 2 CO 3 = mol CO 3 2- x 1 4G-2 (of 12)

10.0 mL of M BaCl 2 are mixed with 20.0 mL of M K 2 SO 4. (a)Find the moles of each ion in the solution. x L solution = mol BaCl mol BaCl 2 ______________________ L solution  mol Ba 2+ and mol Cl - x L solution = mol K 2 SO mol K 2 SO 4 ______________________ L solution  mol K + and mol SO G-3 (of 12)

10.0 mL of M BaCl 2 are mixed with 20.0 mL of M K 2 SO 4. (b)Find the moles of each ion after any reaction. Ba 2+ + SO 4 2- →BaSO 4 Initial moles Reacting moles Final moles  0 mol Ba mol SO mol Cl mol K + 4G-4 (of 12)

10.0 mL of M BaCl 2 are mixed with 20.0 mL of M K 2 SO 4. (c)Find the final molarities of each ion in the solution. = 0 M Ba 2+ 0 mol Ba 2+ ______________________ L solution = M SO mol SO 4 2- _______________________ L solution = M Cl mol Cl - _______________________ L solution = M K mol K + _______________________ L solution 4G-5 (of 12)

20.0 mL of M HCl are mixed with 30.0 mL of M NaOH. (a)Find the moles of each ion in the solution. x L solution = mol HCl mol HCl ___________________ L solution  mol H + and mol Cl - x L solution = mol NaOH mol NaOH ______________________ L solution  mol Na + and mol OH - 4G-6 (of 12)

20.0 mL of M HCl are mixed with 30.0 mL of M NaOH. (b)Find the moles of each ion after any reaction. H + + OH - → H 2 O Initial moles Reacting moles Final moles  0 mol H mol OH mol Cl mol Na + 4G-7 (of 12)

20.0 mL of M HCl are mixed with 30.0 mL of M NaOH. (c)Find the final molarities of each ion in the solution. = 0 M H + 0 mol H + ______________________ L solution = M OH mol OH - _______________________ L solution = M Cl mol Cl - _______________________ L solution = M Na mol Na + _______________________ L solution 4G-8 (of 12)

20.0 mL of M HCl are mixed with 30.0 mL of M NaOH. (d)Find the mass of water produced by the reaction. = g H 2 O mol H 2 O x g H 2 O __________________ 1 mol H 2 O 4G-9 (of 12)

DILUTION CALCULATIONS When a solution is diluted, only solvent is added, so the moles of solute are unchanged mol solute (concentrated) = mol solute (diluted) M C V C = M D V D 4G-10 (of 12)

Calculate the volume of 6.00 M ammonia needed to prepare 250. mL of a M ammonia solution. M C V C = M D V D V C = M D V D _______ M C = (0.100 M)(250. mL) ________________________ (6.00 M) = 4.17 mL M C = V C = 6.00 M ? M D = V D = M 250. mL 4G-11 (of 12)

Calculate the volume of water that must be added to 5.00 mL of concentrated hydrochloric acid (12.1 M) to make the acid 3.00 M. M C V C = M D V D M C V C = V D _______ M D = (12.1 M)(5.00 mL) _______________________ (3.00 M) = 20.2 mL M C = V C = 12.1 M 5.00 mL M D = V D = 3.00 M ? 20.2 mL mL ____________ Volume of dilute solution Volume of concentrated solution 15.2 mLWater that must be added 4G-12 (of 12)

TITRATION – A technique in which one solution is used to analysis another Buret: a solution of 1 reactant of known concentration REACTIONS IN SOLUTION Flask: another reactant of unknown concentration, mass, etc. STANDARD SOLUTION – A solution of known concentration 4H-1 (of 13)

The mass of sodium bicarbonate in an antacid tablet is to be determined. ACID-BASE INDICATOR – A weak organic acid or base that changes color in acidic or basic solutions The tablet is dissolved in water, an acid-base indicator added, and 21.5 mL of a M hydrochloric acid solution produces a color change. NaHCO 3 + HCl →NaCl + H 2 O + CO 2 x g 21.5 mL M 1 mol x 1 mol NaHCO 3 _________________ 1 mol HCl mol HCl x L solution __________________ L solution = g NaHCO 3 x g NaHCO 3 _______________________ mol NaHCO 3 4H-2 (of 13)

x 1 mol O.A.D. ____________________ g O.A.D. A sodium hydroxide solution is to be standardized mL of the sodium hydroxide solution are required to neutralize a solution made with grams of solid H 2 C 2 O 4. 2H 2 O (m = g/mol). NaOH + H 2 C 2 O 4 →. 2H 2 ONa 2 C 2 O 4 + H 2 O 34.2 mL x M g 2 mol 1 mol x 2 mol NaOH _________________ 1 mol O.A.D g O.A.D. = M NaOH x 1 _______________________ L solution 2 24 _ 4H-3 (of 13)

A 10.0 mL aliquot of a solution containing V 2+ ions is acidified, and 32.7 mL of a M MnO 4 - solution produces a light purple color. If the V 2+ was oxidized to V 5+, determine the molarity of the V 2+ in the original solution. 4H-4 (of 13) ( ) x 3 ( ) x 5 MnO 4 - (aq) + V 2+ (aq) → MnO 4 - → Mn V 2+ → V H 2 O 8H + +5e e - Mn 2+ + V

A 10.0 mL aliquot of a solution containing V 2+ ions is acidified, and 32.7 mL of a M MnO 4 - solution produces a light purple color. If the V 2+ was oxidized to V 5+, determine the molarity of the V 2+ in the original solution. 4H-5 (of 13) 3MnO 4 - → 3Mn 2+ 5V 2+ → 5V H 2 O 24H + +15e e - 15e H + + 3MnO V 2+ →3Mn H 2 O + 5V e - MnO 4 - (aq) + V 2+ (aq) → Mn 2+ + V 5+

A 10.0 mL aliquot of a solution containing V 2+ ions is acidified, and 32.7 mL of a M MnO 4 - solution produces a light purple color. If the V 2+ was oxidized to V 5+, determine the molarity of the V 2+ in the original solution mL x M 32.7 mL M 5 mol3 mol x 5 mol V 2+ ________________ 3 mol MnO mol MnO 4 - x L solution _____________________ L solution = M V 2+ x 1 _______________________ L solution 4H-6 (of 13) 3MnO 4 - (aq) + 5V 2+ (aq) → 3Mn 2+ (aq) + 12H 2 O (l) + 5V 5+ (aq)24H + (aq) +

molar mass H 2 X = grams H 2 X _______________ moles H 2 X molar mass H 2 X = grams H 2 X ______________________ ? moles H 2 X Calculate the molar mass of a diprotic acid if grams of it are neutralized by mL of a M sodium hydroxide solution. 4H-7 (of 13)

H 2 X + NaOH →H(OH) + Na 2 X g x mol mL M 1 mol 2 mol 2 x 1 mol H 2 X _______________ 2 mol NaOH mol NaOH x L sol’n _____________________ L sol’n = mol H 2 X 2 Calculate the molar mass of a diprotic acid if grams of it are neutralized by mL of a M sodium hydroxide solution g H 2 X ________________________ mol H 2 X = 146 g/mol 4H-8 (of 13)

The molarity of an aluminum hydroxide solution is to be determined. An acid-base indicator is added to 10.0 mL of the aluminum hydroxide solution, and 12.5 mL of M hydrochloric acid produces a color change. Al(OH) 3 + HCl →AlCl 3 + H(OH) 10.0 mL x M 12.5 mL M 1 mol3 mol 3 x 1 mol Al(OH) 3 _________________ 3 mol HCl mol HCl x L solution __________________ L solution = M Al(OH) 3 x 1 ____________ L 3 4H-9 (of 13)

( ) x 8 Cinnabar ore contains S 2- ions. A g sample of the ore is dissolved in acid, then all the S 2- is oxidized by 20.4 mL of a M Cr 2 O 7 2- solution. Determine the percentage of S 2- in cinnabar ore. 4H-10 (of 13) ( ) x 3 K 2 Cr 2 O 7 (aq) + S 2- (aq) → K + (aq) + Cr 2 O 7 2- (aq) + S 2- (aq) → Cr 2 O 7 2- → Cr S 2- → S H 2 O14H + +6e e - Cr 3+ + S 8 +30

Cinnabar ore contains S 2- ions. A g sample of the ore is dissolved in acid, then all the S 2- is oxidized by 20.4 mL of a M Cr 2 O 7 2- solution. Determine the percentage of S 2- in cinnabar ore. 4H-11 (of 13) K 2 Cr 2 O 7 (aq) + S 2- (aq) → K + (aq) + Cr 2 O 7 2- (aq) + S 2- (aq) → 8Cr 2 O 7 2- → 16Cr S 2- → 3S H 2 O112H + +48e e - 48e H + + 8Cr 2 O S 2- →16Cr H 2 O + 3S e - Cr 3+ + S 8 +30

Cinnabar ore contains S 2- ions. A g sample of the ore is dissolved in acid, then all the S 2- is oxidized by 20.4 mL of a M Cr 2 O 7 2- solution. Determine the percentage of S 2- in cinnabar ore. x g20.4 mL M x 24 mol S 2- _________________ 8 mol Cr 2 O mol Cr 2 O 7 2- x L solution _______________________ L solution = g S 2- x g S 2- _____________ mol S g S 2- x 100 _______________ g ore = 14.1% S 2- in the ore 4H-12 (of 13) 8Cr 2 O 7 2- (aq) + 24S 2- (aq) → 16Cr 3+ (aq) + 56H 2 O (l) + 3S 8 (s)112H + (aq) + 8 mol 24 mol

Calculate the molarity of a sulfuric acid solution if 25.0 mL of it are neutralized by 33.5 mL of a M potassium hydroxide solution. H 2 SO 4 + KOH →H(OH) + K 2 SO mL x M 33.5 mL M 1 mol2 mol 2 x 1 mol H 2 SO 4 _________________ 2 mol KOH mol KOH x L solution ___________________ L solution = M H 2 SO 4 x 1 ____________ L 2 4H-13 (of 13)

MOLAR MASSES AND STOICHIOMETRIC CONVERSIONS 2 mol C (12.01 g/mol)= g 6 mol H (1.008 g/mol)= 6.048g 1 mol O (16.00 g/mol)=16.00 g g Calculate the molar mass of ethanol, C 2 H 5 OH 4I-1 (of 8) g C 2 H 5 OH = 1 mol C 2 H 5 OH

x 1 mol C 2 H 5 OH ______________________ g C 2 H 5 OH Calculate the number of ethanol molecules in 25.0 mL of pure ethanol. The density of the ethanol is g/mL mL C 2 H 5 OH x x molecules C 2 H 5 OH ________________________________________ 1 mol C 2 H 5 OH = 2.58 x molecules C 2 H 5 OH x g C 2 H 5 OH ____________________ 1 mL C 2 H 5 OH g C 2 H 5 OH = 1 mL C 2 H 5 OH 4I-2 (of 8)

x g C 2 H 5 OH ____________________ 1 mL C 2 H 5 OH x 1 mol C 2 H 5 OH ______________________ g C 2 H 5 OH Calculate the number of carbon atoms in a 10.0 mL sample of pure ethanol mL C 2 H 5 OH x 2 mol C __________________ 1 mol C 2 H 5 OH = 2.06 x atoms C x x atoms C ___________________________ 1 mol C 4I-3 (of 8)

x 40. mL C 2 H 5 OH ____________________ 100 mL vodka x 1 mol C 2 H 5 OH ______________________ g C 2 H 5 OH Calculate the number of ethanol molecules in 45.0 mL of 80. proof vodka. The density of the vodka is 0.92 g/mL mL vodka x x molecules C 2 H 5 OH ________________________________________ 1 mol C 2 H 5 OH = 1.9 x molecules C 2 H 5 OH x g C 2 H 5 OH ____________________ 1 mL C 2 H 5 OH 80. Proof vodka = 40.% C 2 H 5 OH by volume 100 mL vodka = 40. mL C 2 H 5 OH 4I-4 (of 8)

x g C 2 H 5 OH _______________________ mol C 2 H 5 OH Calculate the mass of one ethanol molecule, in grams. = x g x mol C 2 H 5 OH ________________________________________ x molecules C 2 H 5 OH 4I-5 (of 8) 1 molecule C 2 H 5 OH

x 1 mol O ____________ g O A metal oxide with the formula M 2 O 3 is 29.0% oxygen by mass. Calculate the molar mass of metal M g O x 2 mol M __________ 3 mol O = 58.8 g/mol 71.0 g M _________________ mol M 4I-6 (of 8) g M mol M Molar Mass of M = = 71.0 g M ? mol M = mol M

1 mol Na (22.99 g/mol)= g 1 mol N (14.01 g/mol)= g 3 mol O (16.00 g/mol)=48.00 g g THEORETICAL PERCENT COMPOSITION OF COMPOUNDS BY MASS NaNO 3 Calculate the percent composition by mass of sodium nitrate g Na  100 ___________________ g NaNO 3 % Na == % Na g O  100 ___________________ g NaNO 3 % O == % O g N  100 ___________________ g NaNO 3 % N == % N 4I-7 (of 8)

BaCl 2. 2H 2 O 1 mol Ba (137.3 g/mol)= g 2 mol Cl (35.45 g/mol)= g 2 mol H 2 O ( g/mol)=36.032g g Calculate the percentage by mass of water in barium chloride dihydrate g H 2 O  100 ____________________________ g BaCl 2. 2H 2 O % H 2 O == % H 2 O 4I-8 (of 8)

EMPIRICAL AND MOLECULAR FORMULA CALCULATIONS When a sample of a hydrocarbon is burned, 8.45 g CO 2 and 1.73 g H 2 O are produced. Calculate the empirical formula of the hydrocarbon. C x H y + O 2 →CO 2 + H 2 O 8.45 g CO 2 = g C x g C ________________ g CO g H 2 O= g Hx g H ________________ g H 2 O 4J-1 (of 9)

x 1 mol C _____________ g C = mol C g C x 1 mol H ____________ g H = mol H g H mol C _________________ mol H _________________ = 1.00 mol C= 1.00 mol H Empirical formula: CH EMPIRICAL AND MOLECULAR FORMULA CALCULATIONS When a sample of a hydrocarbon is burned, 8.45 g CO 2 and 1.73 g H 2 O are produced. Calculate the empirical formula of the hydrocarbon. 4J-2 (of 9)

A borane is any compound composed of boron and hydrogen. When a sample of a borane is burned, g B 2 O 3 and g H 2 O are produced. Calculate the empirical formula of the borane. B x H y + O 2 →B 2 O 3 + H 2 O g B 2 O 3 = g B x g B ________________ g B 2 O g H 2 O = g H x g H ________________ g H 2 O 4J-3 (of 9)

x 1 mol B _____________ g B = mol B g B x 1 mol H _____________ g H = mol H g H mol B ___________________ mol H _________________ = mol B= mol H Empirical formula: B 3 H 11 A borane is any compound composed of boron and hydrogen. When a sample of a borane is burned, g B 2 O 3 and g H 2 O are produced. Calculate the empirical formula of the borane. 4J-4 (of 9) x 3

When a 3.84 g sample of a compound containing C, H, and N is combusted, 7.34 g CO 2 and 2.51 g H 2 O are collected. Calculate the empirical formula of the compound. C x H y N z + O 2 →CO 2 + H 2 O + N a O b 7.34 g CO 2 = g C x g C ________________ g CO g H 2 O = g H x g H _____+__________ g H 2 O 3.84 g C x H y N z g C g H ________________________ g N 4J-5 (of 9)

When a 3.84 g sample of a compound containing C, H, and N is combusted, 7.34 g CO 2 and 2.51 g H 2 O are collected. Calculate the empirical formula of the compound. x 1 mol C _____________ g C = mol C g C x 1 mol H ____________ g H = mol H g H mol C _________________ mol H _________________ = 1.50 mol C= 2.51 mol H Empirical formula: C 3 H 5 N 2 x 1 mol N _____________ g N = mol N g N mol N ________________ = 1.00 mol N 4J-6 (of 9)

When a 2.75 g sample of a compound containing C, H, and O is combusted, 5.49 g CO 2 and 2.25 g H 2 O are collected. Calculate the empirical formula of the compound. C x H y O z + O 2 →CO 2 + H 2 O 5.49 g CO 2 = g C x g C ________________ g CO g H 2 O = g H x g H _________________ g H 2 O 2.75 g C x H y O z g C g H ________________________ g O 4J-7 (of 9)

When a 2.75 g sample of a compound containing C, H, and O is combusted, 5.49 g CO 2 and 2.25 g H 2 O are collected. Calculate the empirical formula of the compound. x 1 mol C ____________ g C = mol C g C x 1 mol H ____________ g H = mol H g H mol C _________________ mol H _________________ = 1.99 mol C= 4.00 mol H Empirical formula: C 2 H 4 O x 1 mol O _____________ g O = mol O g O mol O __________________ = 1.00 mol O 4J-8 (of 9)

C2H4OC2H4O 2 mol C (12.01 g/mol)= g 4 mol H (1.008 g/mol)=4.032g 1 mol O (16.00 g/mol)= g g 90 g/mol ________________ g/mol ≈ 2 Molecular formula: C 4 H 8 O 2 Calculate the molecular formula of the previous compound if it has a molar mass of about 90 g/mol. 4J-9 (of 9)