1、Chemical Quantities and Aqueous Reactions,Chapter 4,Outline Stoichiometry Percent Yield Limiting Reactant Solution Stoichiometry Molarity Dilutions,Classifying Reactions by Type of Chemistry,Classifying Reactions by Type of Chemistry,Precipitation AX + BZ AZ + BX (s) Acid Base HX +BOH BX +H2O (l) Ga
2、s Evolution H2X + BS H2S (g) + BX H2X + BCO3 H2O + CO2 (g) + BX H2X + BSO3 H2O + SO2 (g) + BX NH4X + BOH H2O + NH3 (g) + BX Oxidation Reduction A2+ + B A + B2+ Combustion CxHxOx+O2CO2 (g) + H2O (g),Classifying Reactions by what Atoms Do,Classifying Reactions by what Atoms Do,Combination/Synthesis A
3、+ Z AZ Decomposition AZ A + Z Single Displacement A + BZ AZ + B Double displacement AX + BZ AZ + BX Neutralization HX +BOH BX +H2O Gas Forming Reactions/Precipitation Reactions,Chapter 4: Examples Stoichiometry,Given the unbalanced reaction: S (s) + O2 (g) + H2 O (l) H2 SO4 (aq) Calculate the mass o
4、f sulfuric acid in kg that can be produced from 25 kg of sulfur. If 54.629 kg of sulfuric acid is experimentally obtained, what is the percent yield?,Chapter 4: Examples Stoichiometry,The first stage in the production of nitric acid is the oxidation of ammonia in the presence of a platinum catalysis
5、 to produce gaseous nitrogen monoxide and water. Calculate the mass in grams of nitrogen monoxide that is produced from the reaction of 600. L of oxygen gas with excess ammonia, assuming 90.0% yield. The density of oxygen gas under the reaction conditions is 1.43 g/L.,Chapter 4: Examples Limiting Re
6、actant,In the Haber Process ammonia gas is produced by the reaction of nitrogen and hydrogen gases. Consider a flask with 5 nitrogen molecules and 9 hydrogen molecules. What is the limiting reactant? Use an ICE table. How many molecules of ammonia are produced? How many molecules of the excess reage
7、nt are left?,Chapter 4: Examples Limiting Reactant,Lithium metal is the only member of the alkali metals that reacts directly with nitrogen gas to produce a nitride. What mass of lithium nitride can form, if 48.0 g of lithium and 1.00 x 1024 molecules of nitrogen gas react? Use an ICE table. What is
8、 the mass of excess reactant in the system?,Chapter 4: Examples Limiting Reactant,A mixture of 87.05% pure butane of mass 4.50 g and 11.1 L of oxygen gas (density 1.43 g/L) reacts as follows: C4H10 (g) + O2 (g) CO2 (g) + H2O (g) and 10.7 g of carbon dioxide was collected. Use an ICE table to find th
9、e limiting reactant. What is the percent yield of carbon dioxide?,What is the difference?,How are solutions quantified?,Chapter 4: Examples Solutions,A student prepared a solution of barium hydroxide by adding 2.577 g of the solid to a 250.0 mL volumetric flask and adding water to the mark. What is
10、the molarity of the solution? Some of this barium hydroxide solution is transferred to a buret. What volume of solution should the student transfer to obtain 3.5 mmoles of hydroxide ions?,How does concentration change during a dilution?,Chapter 4: Examples Dilutions,A 0.752 M ferric nitrate solution
11、 is diluted by taking 5.00 mL and adding it to a 25.00 mL volumetric flask. What is the concentration of nitrate ions in the new solution?,Stoichiometry Road Map,a A b B,mass A mass B,volume A (l) volume B(l),Pure Substance,Solution,Volume A(g) Volume B(g),M A(aq) M B(aq),MM,MM,density,density,equat
12、ion,equation,22.4 L,22.4 L,25,Tro: Chemistry: A Molecular Approach, 2/e,Chapter 4: Examples Solution Stoichiometry,The odor of skunk is caused by chemical compounds called thiols. These compounds, of which butanethiol (C4H10S) is a representative example, can be deodorized according to the following
13、 reaction with household bleach: 2 C4H10S (l) + NaOCl (aq) C8H18S2 (aq) + NaCl (aq) + H2O (l) How many grams of butanethiol can be deodorized by 5.00 mL of 0.0985 M sodium hypochlorite?,Chapter 4: Examples Solution Stoichiometry,What is the concentration of potassium permanganate solution if 22.35 m
14、L is titrated with 0.5170 g oxalic acid dihydrate? Given: 5 H2C2O4 (aq) + 2 KMnO4 (aq) + 3 H2SO4 (aq) 10 CO2 (g) + 2 MnSO4 (aq) + 2 K2SO4 (aq) + 8 H2O (l),Chapter 4: Examples Solution Stoichiometry,A 35.47 mL sample of 0.2430 M H2SO4 is mixed with 65.35 mL of a 0.4199 M sample of KOH. Determine the
15、concentration of all ions in solution, the pH, and pOH.,Chapter 4: Examples Solution Stoichiometry,Suppose that 257.0 mL of a 0.2500 M barium nitrate solution is mixed with 450.0 mL of a 0.6220 M sodium sulfate solution. Write the balanced molecular, total ionic, and net ionic equations. Calculate t
16、he mass of product produced. Use the net ionic equation and an ICE table. Inventory the ions in the solution after the completion of the reaction (i.e. Calculate the molarity of each ion in the solution at the end of the reaction).,Chapter 4 Example Stoichiometry Mixture Problems,A 3.20 g sample of
17、a mixture of sodium chloride and calcium chloride is dissolved in water and heated with excess silver nitrate solution. All of the chloride in the mixture is converted to a precipitate of silver chloride: Ag+ (aq) + Cl- (aq) AgCl (s)The precipitate has a mass of 7.94 g. Calculate the mass of sodium
18、chloride in the original mixture.,Chapter 4 Example Stoichiometry Mixture Problems,A 2.00 g sample of a mixture of sodium chloride and sodium bromide is found to contain 0.750 g of sodium. What is the fraction of sodium chloride in the mixture?,Chapter 18.2,Balancing Oxidation-Reduction Equations,Ox
19、idation-Reduction Reactions Oxidation Numbers Half-Reactions Redox Titrations,OXIDATION STATE,Rules for Assigning Oxidation States: The oxidation number of all atoms adds up to the charge on the molecule or ion. The oxidation state of an element is zero. i.e. Na(s), K(s), Hg(l), Ag(s); these can als
20、o be written as Na0, K0, etc. diatomic molecules: H2 (g), N2 (g), F2 (g), O2 (g), I2 (s), Cl2 (g), Br2 (l), (mnemonic: Have No Fear Of Ice Cold Beer) The oxidation number of: an alkali metal is +1an alkaline earth metal is +2metals in group IIIA (B, Al, etc) is +3 The oxidation number of hydrogen +1
21、 in covalent compounds with nonmetals: ex) CH4 (g), HCl (aq), NH3 (g), H2SO4 (aq), etc 1 when combined with metals (especially alkali & alkaline earth metals): ex) NaH, LiH, AlH3 Halides (F, Cl, Br, and I) usually have an oxidation number of 1. The fluoride ion has a -1 oxidation state, except when
22、paired with oxygen. The oxidation number of oxygen and other group VIA elements is 2 in covalent compounds. Exception: oxygen has an oxidation state of 1 in peroxides (H2O2 or Na2O2 where oxygen is O22-) and in superoxides -1/2 (NaO2 where oxygen is O2-). Non-integer oxidation states do exist ex) In
23、 Fe3O4, iron has an oxidation state of +8/3,BALANCING HALF REACTIONS,Step 1: Write the skeletal net ionic equation. (This is usually given.) Step 2: Make two half reactions, one for the species being oxidized the other for the species being reduced. Step 3: Balance all atoms except for the hydrogen
24、and oxygen atoms. Step 4: Balance the hydrogen and oxygen atoms In acidic conditions: Balance the hydrogen atoms by adding hydrogen ions (H+) Balance the oxygen atoms by adding water (H2O) In basic conditions: Balance the oxygen atoms by adding hydroxide ions (OH-) Balance the hydrogen atoms by addi
25、ng water (H2O) Step 5: To balance charge add electrons to the side with greater positive charge. Step 6: Multiply each half reaction by an appropriate whole number so that the number of electron in each half reaction is equal. Step 7: Add the two balanced half reactions together, and cancel out spec
26、ies that appear on both sides of the equation. Step 8: Check to make sure that your reaction is balanced.,Chapter 18.2: Examples Balancing Redox Equations,The products of the oxidation of bromide ions by permanganate ions in basic solution are solid manganese(IV) oxide and bromate ions. Balance the
27、chemical equation for the reaction.,Chapter 18.2: Examples Balancing Redox Equations,An alkaline solution of hypochlorite ions react with solid chromium(III) hydroxide to produce chromate ions and chloride ions. Write the balanced chemical equation for the reaction.,Chapter 18.2: Examples Balancing
28、Redox Equations,When acidified potassium permanganate is mixed with a solution of sulfurous acid, sulfuric acid, and manganese(II) ions are produced. Write the balanced chemical equation for the reaction. In acidic solution sulfurous acid is present as the nonionized molecules and sulfuric acid is p
29、resent as bisulfate and hydrogen ions.,Chapter 18.2: Examples Balancing Redox Equations,A typical lead battery has six voltaic cells linked together. Each of the cells consists of a lead plate that acts as the anode (oxidation) and a lead(IV) oxide plate that acts as the cathode (reduction). Both ha
30、lf reactions contain a sulfuric acid solution. Write the overall cell reaction.,Chapter 18.2: Examples Redox Titrations,If 10.00 mL of a ferrous chloride solution of unknown molarity is diluted with 90.00 mL of 1.0 M hydrochloric acid and 5 drops of barium diphenylaminesulfonate is added and it take
31、s 27.30 mL of 0.01552 M potassium dichromate to reach the end point. What is the concentration of the ferrous chloride? Given the unbalanced equation:,Chapter 18.2: Examples Redox Titrations,If 15.00 mL of a ferrous ion solution is diluted with base and then titration with 42.57 mL of 0.1155 M potassium permanganate. What is the molarity of the ferrous ions? Given the unbalanced equation:,
