CM1011 Exp4_Types of Rxn & Rxn Equations_Fa23

Name ___________________________________________ Section ________________ Experiment 4 Types of Reaction and Reaction Equations CM1011 Fall 2023 1 Types of Reaction and Reaction Equations In your text (Chang and Goldsby 7 th Ed): 4.2 – 4.4 Precipitation Reactions, Acid-Base Reactions, Oxidation-Reduction Reactions Background: Classifying chemical reactions is extremely useful for organizing, understanding, and predicting the behavior of huge numbers of chemical reactions. The classifications used in this experiment belong to a commonly used organization scheme, but this is not the only classification system. The classification system highlighted in this lab emphasizes the form of the reaction: Combination (or synthesis) A + B à AB Decomposition AB à A + B Single displacement (or substitution) A + BX à AX + B Double displacement (or metathesis) AB + CD à AD + CB Other reaction classifications emphasize the mechanism of the reaction, for example: Name Mechanism Notes Redox (oxidation- reduction) Electron ( ࠵? " transfer) Oxidation states change Acid-Base (Neutralization) 1. Acid + base à salt + water HA + BOH à AB + H $ O (Arrhenius definition, H & or OH " ) Arrhenius mechanism is a specific type of double displacement reaction. 2. Proton ( H & ) transfer (Bronsted definition, very general) Acid is H & donor Base is H & acceptor 3. ࠵? " pair association (Lewis definition, most general) Acid is ࠵? " pair acceptor Base is ࠵? " pair donor Other reaction classifications emphasize the product of the reaction, for example gas formation and precipitation reactions . Precipitation is the formation of solid product from fluid reactants (liquid, gas or species in solution). Gas formation implies the formation of insoluble gas, so that it escapes from the reaction mixture – the gas bubbles out of the reaction. Commonly encountered subsets of or variations on some of the classes listed above are given specific classifications. A combustion reaction is a specific type of redox reaction in which a compound reacts exothermically with an oxidizing agent to form oxidized products. A very common type of combustion reaction is the reaction of a hydrocarbon and O $ to yield CO $ and water.

Name ___________________________________________ Section ________________ Experiment 4 Types of Reaction and Reaction Equations CM1011 Fall 2023 2 An example of this type of combustion reaction is the complete combustion of naphthalene: C () H * + 12 O $ à 10 CO $ + 4 H $ O Combustion reactions are not limited to this very common type. Hydrolysis involves the decomposition of both a chemical compound and water, with the fragments recombining, of the form: CD + H $ O à CH + DOH Where CD can be either an ionic or a molecular compound. This is a common reaction in organic chemistry. In your text, pp. 138-141, some very common single displacement reactions are named by what is specifically displaced, i.e. hydrogen displacement, metal displacement , and halogen displacement . Finally, note that a particular reaction can be classified in more than one way. For example, Zn (s) + 2 HCl (aq) à Zn Cl $ (aq) + H $ (g) is a single displacement reaction, specifically a hydrogen displacement reaction, with the Zn displacing the H. it is also a redox reaction, with Zn oxidized to Zn $& and the two H & reduced to H $ . It is also a gas formation reaction, cf. pictures of the bubbling reaction mixture in your text, p. 142. Combination Reactions: A + B à AB, where A and B can be either elements or compounds, combining to form a compound. Also called a synthesis reaction . Equation Reaction Reference/notes 1 Mg (s) + O $ (g) à 2 MgO (s) Exp. 4 and Text, 4.4 2 2 Ca (s) + O $ (g) à 2 CaO (s) 3 8 Mg (s) + S * (s) à 8 MgS (s) 4 CaO (s) + H 2 O (l) à Ca(OH) 2 (aq) 5 S (s) + O $ (g) à SO $ Text, last half of section 4.4 6 H $ (g) + Cl $ (g) à 2 HCl (g) Decomposition Reactions: AB à A + B, where a substance decomposes to its elements or simpler compounds, usually due to the application of heat (may be shown as ∆ above the arrow). Equation Reaction Reference/notes 7 2 HgO (s) à 2 Hg (l) + O 2 (g) Text, last half of section 4.4 8 2 KCl O 1 (s) à 2 KCl (s) + 3 O $ (g) Text, last half of section 4.4 9 2 H $ O (l) à 2 H $ (g) + O $ (g) Electrolysis of water 10 BaC O 1 (s) à BaO (s) + C O $ (g) Carbonate decomposition 11 Ba Cl $ ∙ 2 H $ O (s) à Ba Cl $ (s) + 2 H $ O (l) Text, end of section 2.7 Barium chloride dihydrate à anhydrous barium chloride + water (Hydrates are ionic solids having specific number of water molecules loosely attached to them in fixed stoichiometric ratios. Example, CuS O 3 ∙ 5H $ O , copper sulfate pentahydrate, etc.)

Name ___________________________________________ Section ________________ Experiment 4 Types of Reaction and Reaction Equations CM1011 Fall 2023 4 Arrhenius acid-base reaction, or a solid, as in a precipitation reaction . Just as a precipitate will separate from the surrounding mixture, the analogous species in an Arrhenius acid-base reaction is the covalent water molecule, and the gas in a gas formation reaction. Equation Reaction Reference/notes 15 Na $ S + 2 HCl (aq) à 2 NaCl (aq) + H $ S (g) Gas formation Text, end of section 4.3 16 HNO 3 (aq) + KOH (aq) à KNO 3 (aq) + H 2 O (l) Arrhenius acid-base Text p. 133 17 BaCl $ (aq) + Na $ SO 3 (aq) à BaSO 3 (s) + 2 NaCl (aq) Precipitation, text sect. 4.2 Just as with the precipitation reaction, the other double displacement reactions can be written in molecular, full ionic, and net ionic forms. For example, Eq. 16, the Arrhenius acid-base reaction (with H & , OH " ions) can be written: Molecular HNO 1 (aq) + KOH (aq) à H $ O (l) + KNO 1 (aq) Full ionic H & (aq) + NO 1 " (aq) + K & (aq) + OH " (aq) à H $ O (l) + K & (aq) + NO 1 " (aq) Net ionic H & (aq) + OH " (aq) à H $ O (1) The net ionic equation for an Arrhenius acid-base reaction highlights that the core of the reaction is the delivery of H & by the acid and the delivery of OH " by the base, which combine to form water. The acid could be HCl, HNO 1 , H $ SO 3 , etc. and the base could be NaOH, KOH, Ba(OH ) $ , etc. One can predict the precipitate for a precipitation reaction by using some general solubility rules, listed below, Table 1 . For example, if aqueous AgNO 1 and Na $ SO 3 are mixed, what happens? The ions in solution will be Ag & (aq), NO 1 " (aq), Na & (aq) , and SO 3 $" (aq) . Since all of the ions are soluble in their initial pairing, a reaction (if there is one) will occur if the ions "swap partners". Therefore, the possible products are Ag $ SO 3 and NaNO 1 . Examining Table 1, we find that all sulfates, with few exceptions, are soluble. Ag is one of the exceptions, so Ag $ SO 3 will precipitate as a solid. There are no exceptions regarding the solubility of both alkali metals and nitrates, so by either test, NaNO 1 will remain in solution. The skeletal (unbalanced) reaction equation, then, is: AgNO 1 (aq) + Na $ SO 3 (aq) à Ag $ SO 3 (s) + NaNO 1 (aq) Now, balance the equation, giving the molecular equation. Molecular 2 AgNO 1 (aq) + Na $ SO 3 (aq) à Ag $ SO 3 (s) + 2 NaNO 1 (aq) Next, break the species in the balanced molecular equation into all the individual ions, and you have the full ionic equation: Full ionic 2 Ag & (aq) + 2 NO 1 " (aq) + 2 Na & (aq) + SO 3 $" (aq) à Ag $ SO 3 (s) + 2 Na & (aq) + 2 NO 1 " (aq)

Name ___________________________________________ Section ________________ Experiment 4 Types of Reaction and Reaction Equations CM1011 Fall 2023 5 Note that the precipitate, Ag $ SO 3 (s), does NOT break into individual ions. It holds together as an ionic solid, and hence is written as a single neutral compound. Finally, cancel out the spectator ions, Na & (aq) and NO 1 " (aq), to yield: Net ionic 2 Ag & (aq) + SO 3 $" (aq) à Ag $ SO 3 (s) Table 1: Solubility Rules for common ionic compounds in water at 25 ° C Soluble Compounds Exceptions Compounds containing alkali metal ions and N H 3 & none N O 1 " , HC O 1 " , Cl O 1 " , Cl O 3 " , C H 1 C O $ " None Cl " , Br " , I " Halides of Ag & , Hg $ $& , Pb & S O 3 $" Sulfates of Ag & , Ca $& , Sr $& , Ba $& , Hg $& , Pb $& Insoluble Compounds Exceptions C O 1 $" , P O 3 1" , Cr O 3 $" , S $" , C $ O 3 " Compounds containing alkali metal ions and N H 3 & O H " , O $" Compounds containing alkali metal ions, N H 3 & and Ba $& Note: Solubility is not a light switch, ON/OFF, soluble/insoluble. Generally, and approximately , SOLUBLE means a compound’s solubility is > 1 g / 100 mL INSOLUBLE means a compound’s solubility is < 0.1 g / 100 mL SPARINGLY SOLUBLE means solubility between these limits For example, Ca SO 3 has a solubility in water at 20 ° C of 0.21 g/100 mL, and is listed as sparingly soluble in some texts, but insoluble in others (such as ours).

Name ___________________________________________ Section ________________ Experiment 4 Types of Reaction and Reaction Equations CM1011 Fall 2023 7 For all reactions: Record the appearance of the individual reactants BEFORE mixing, perform the procedure, and record your observations. Record all observations and descriptions IN INK on your Data Sheet at the time of observation. Dispose of all solids and solutions in the appropriate containers in the waste disposal hood by the door. The experiments are grouped into Part A, those that can be done on the bench at your normal work station, and Part B, those to be done in the hood, using a Bunsen burner. About half of the class should start Part A first, and the other half should start Part B, so there is not a pileup of students all wanting to use the hoods at the same time. Once the ring stands, iron rings, clay triangles and Bunsen burners are set up in the hoods, leave them set up for use by other students. Part A, on the bench: I. Reacting Mg with HCl Solution Caution: Both Mg and the gas produced by the reaction of Mg and HCl are flammable. Be sure that there are no open flames in the area where you are performing this reaction. Transfer a small piece of Mg ribbon or several pieces of Mg turnings to the bottom of a clean test tube and add approximately 2 mL of 0.10 M HCl, using a 10-mL graduated cylinder. Swirl the test tube to mix the contents and record your observations. II. Reacting Pb(N ࠵? ࠵? ) ࠵? Solution with KI Solution Caution: Pb (NO 1 ) $ is toxic, an irritant, and an oxidant. Notify your laboratory instructor immediately if you spill any Pb (NO 1 ) $ solution. Transfer 10 drops of 0.10 M Pb (NO 1 ) $ into a clean test tube. Add 2 drops of 0.10 M KI(aq) and record your observations. III. Reacting HCl Solution with NaOH Solution Caution: Both NaOH and HCl solutions are toxic, corrosive, and can cause skin burns. If you spill either solution, notify your laboratory instructor immediately. Transfer about 2 mL of 0.10 M NaOH into test tube. Add one drop of phenolphthalein solution, an acid—base indicator, to the NaOH solution in the test tube and describe the appearance. Measure out about 3 mL of 0.10 M HCl into a graduated cylinder. Add one drop of phenolphthalein solution and describe the appearance of solution. Carefully pour 1 mL of the HCl—phenolphthalein solution into the test tube containing the NaOH solution and pour the remaining 2 mL of HCl solution into either a test tube or small beaker, so you can use an eyedropper to transfer small quantities. (Graduated cylinders are usually too tall to get at the liquid with an eyedropper.) Record your observations after the addition of 1 mL HCl to the NaOH. Keep adding more HCl solution dropwise into the NaOH solution until you see evidence that a reaction has occurred, or until you transfer all of the HCl solution into the NaOH test tube. Record your evidence, if any, that a reaction has occurred.

Name ___________________________________________ Section ________________ Experiment 4 Types of Reaction and Reaction Equations CM1011 Fall 2023 8 IV. Reacting CuS ࠵? ࠵? Solution with Steel Wool (Fe) Obtain an amount of steel wool (Fe) that is about the size of a pencil eraser. Use a clean, dry glass stirring rod to carefully slide the steel wool to the bottom of a clean, dry, 20 • 150-mm test tube and add about 2 mL of 0.10 M CuS O 3 . Describe the appearance of reaction mixture. V. Reacting Fe ࠵?࠵? ࠵? Solution with NaOH Solution Obtain about 1 mL of 0.10 M Fe Cl 1 into a test tube and transfer about 1 mL of 0.10 M NaOH. Describe the appearance of the reaction mixture. Part B, in the hood: VI. Heating Steel Wool (Fe) with Sulfur ( ࠵? ࠵? ) Caution: The fumes from burning S * are toxic and irritating. Avoid inhaling the fumes. Perform this reaction in the hood. Place enough flattened steel wool in a porcelain crucible to cover the bottom. Fill the end of a clean, dry scoopula with powdered sulfur ( S * ) to about the length of the first joint on your pinkie finger and sprinkle it over the steel wool. Place the cover flat on the crucible (closed), not cocked to one side. Working in the hood, set the covered crucible with its contents in a clay triangle resting on an iron ring attached to a ring stand, as shown in Fig. 1. This is the same setup you used in Exp. 4, except it is done in the hood and the cover is set flat. (In Exp. 4, you cocked the cover to one side to leave an opening to the air.) Strongly heat the Fe and S * mixture for 5 min. Using crucible tongs, carefully lift the hot crucible cover and look for evidence of unreacted S * , in the crucible. If you find any unreacted S 8 , cover the crucible and reheat for a few more minutes. Fig. 1 Keep heating and checking until all visible evidence of unreacted S * has disappeared. Removing the crucible from the hot clay triangle and iron ring, place the crucible on a piece of wire gauze to cool. Using a clean glass stirring rod, gently crush the reaction product and record your observations of the appearance. VII. Heating Copper (Cu) with Atmospheric ࠵? ࠵? You are going to repeat the procedure of Part VI, Heating Steel Wool (Fe) with Sulfur ( S * ), substituting Cu for Fe and atmospheric O $ for S * . Since the O $ comes from the air, you do not have to put anything in the crucible except copper mesh and you do not use a crucible cover at all; leave the cover off and the crucible open to the air.

Name ___________________________________________ Section ________________ Experiment 4 Types of Reaction and Reaction Equations CM1011 Fall 2023 10 Fig. 3a Bad Technique – sniffing directly Fig. 3b Good Technique – wafting Caution: wash your hands thoroughly with soap and water before leaving the laboratory.

Name ___________________________________________ Section ________________ Experiment 4 Types of Reaction and Reaction Equations CM1011 Fall 2023 11 Pre-Laboratory Assignment 1. All of the reactions of Part A (I. - V.) are to be done on the lab bench, and those of Part B (VI.- IX.) all use a Bunsen burner with an open flame and are to be done in the hood. a. Which reaction in Part A must be kept away from an open flame, for safety reasons? What is the hazard? b. Which reaction(s) in Part B must be done in the hood, for safety reasons? What are the hazards? 2. Aqueous solutions of barium chloride, BaCl 2 , and ammonium sulfate, (NH 4 ) 2 SO 4 , are mixed. a. Write the balanced chemical equation for this reaction. In the following forms: i. Molecular ii. Full ionic iii. Net ionic b. What are the spectator ions? c. What type of reaction is this? (circle one) Combination Decomposition Single Displacement Double Displacement d. Which of the following alternative classification can also be used for this reaction? (circle one) Precipitation reaction Acid-base reaction Oxidation-reduction reaction Pre-Lab ______/20 Data ______/60 Post-Lab ______/20 Safety (deduction) - ____ Legibility (deduction) - ____ Tardiness (deduction) - ____ TOTAL ______/100 Grading

Name ___________________________________________ Section ________________ Experiment 4 Types of Reaction and Reaction Equations CM1011 Fall 2023 13 DATA SHEET Write in INK Instructor’s Initials: ____ I. Reacting Mg with HCl solution Appearance of Mg: Appearance of HCl solution: Appearance of chemical reaction: II. Reacting Pb(N ࠵? ࠵? ) ࠵? with KI solution Appearance of Pb(N O 1 ) $ solution: Appearance of KI solution: Appearance of reaction mixture: III. Reacting HCl solution with NaOH Solution Appearance of NaOH solution: Appearance of NaOH solution with phenolphthalein solution added: Appearance of HCl solution: Appearance of HCl solution in graduated cylinder with phenolphthalein solution added: Appearance of NaOH solution after 1 mL of HCl was added: After more HCl was added: After all HCl was added:

Name ___________________________________________ Section ________________ Experiment 4 Types of Reaction and Reaction Equations CM1011 Fall 2023 14 DATA SHEET Write in INK Instructor’s Initials: ____ IV. Reacting CuS ࠵? ࠵? Solution with Steel Wool (Fe) Appearance of steel wool (Fe) before the reaction: Appearance of Cu SO 3 solution before the reaction: Appearance of steel wool after the reaction has occurred: Appearance of Cu SO 3 solution after the reaction has occurred: V. Reacting Fe ࠵?࠵? ࠵? Solution with NaOH Solution Appearance of Fe Cl 1 solution: Appearance of NaOH solution: Appearance of reaction mixture: VI. Heating Steel Wool (Fe) with ࠵? ࠵? : Appearance of steel wool (Fe): Appearance of S * : Appearance of reaction product:

Name ___________________________________________ Section ________________ Experiment 4 Types of Reaction and Reaction Equations CM1011 Fall 2023 16 Analysis and classification . For "general reaction type", classify the reactions as Combination, Decomposition, Single Displacement, or Double Displacement. (Make sure to include the states of matter of each substance in the reaction.) I. Reacting Mg with HCl Solution chemical equation: ______________________________________________________________ complete ionic equation: _________________________________________________________ net ionic equation: ________________________________________ general reaction type: ____________________________ II. Reacting Pb(N ࠵? ࠵? ) ࠵? solution with KI Solution chemical equation: ______________________________________________________________ complete ionic equation: _________________________________________________________ net ionic equation: ________________________________________ general reaction type: ____________________________ III. Reacting HCl Solution with NaOH Solution chemical equation: ______________________________________________________________ complete ionic equation: _________________________________________________________ net ionic equation: ________________________________________ general reaction type: ____________________________

Name ___________________________________________ Section ________________ Experiment 4 Types of Reaction and Reaction Equations CM1011 Fall 2023 17 IV. Reacting CuS ࠵? ࠵? Solution with Steel Wool (Fe) chemical equation: ______________________________________________________________ complete ionic equation: _________________________________________________________ net ionic equation: ________________________________________ general reaction type: ____________________________ V. Reacting Fe ࠵?࠵? ࠵? Solution with NaOH Solution chemical equation: ______________________________________________________________ complete ionic equation: _________________________________________________________ net ionic equation: ________________________________________ general reaction type: ____________________________ VI. Heating Steel Wool (Fe) with ࠵? ࠵? : chemical equation: ______________________________________________________________ general reaction type: ____________________________ VII. Heating Cu with Atmospheric ࠵? ࠵? chemical equation: ______________________________________________________________ general reaction type: ____________________________

Name ___________________________________________ Section ________________ Experiment 4 Types of Reaction and Reaction Equations CM1011 Fall 2023 19 Post-Laboratory Questions 1. In the Analysis and Classification section, each of the reactions were classified under the general reaction scheme emphasizing the form of the reaction as Combination, Decomposition, Single Displacement, Displacement, or Double Displacement. Now, referring to the alternative classification schemes discussed in the Background, classify the reaction as : Redox (oxidation-reduction) Gas formation Acid-base (neutralization) Precipitation Combustion reaction Hydrolysis Hydrogen displacement Halogen displacement Metal displacement Some reactions will have more than one answer. I. Reacting Mg with HCl Solution II. Reacting Pb(N ࠵? ࠵? ) ࠵? solution with KI Solution III. Reacting HCl Solution with NaOH Solution IV. Reacting CuS ࠵? ࠵? Solution with Steel Wool (Fe) V. Reacting Fe ࠵?࠵? ࠵? Solution with NaOH Solution VI. Heating Steel Wool (Fe) with ࠵? ࠵? VII. Heating Cu with Atmospheric ࠵? ࠵? VIII. Heating Cu ࠵?࠵? ࠵? ∙ 5 ࠵? ࠵? ࠵? IX. Heating (࠵?࠵? ࠵? ) ࠵? C ࠵? ࠵?

Name ___________________________________________ Section ________________ Experiment 4 Types of Reaction and Reaction Equations CM1011 Fall 2023 20 2. For each of the reaction identified as redox reactions, identify the species being OXIDIZED and write the oxidation half reaction. Using Eq. 13 as an example: Sn (s) + 2 AgN O 1 (aq) à Sn (NO 1 ) $ (aq) + 2 Ag (s) Answer: Sn(s) is reduced to Sn 2+ (aq) Sn(s) à Sn 2+ (aq) + ࠵?࠵? " Experimental redox reactions and species being oxidized: 3. When hydrofluoric acid, HF, reacts with NaOH, is the net ionic equation the same as the one you wrote for reaction III between hydrochloric acid, HCl, and NaOH? Why or why not?