CM1011 Exp4_Types of Rxn & Rxn Equations_Fa23

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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 3 Single-Displacement Reactions: A + BX à AX + B, where one element is replaced (displaced) by another in a compound. Equation Reaction Reference/notes 12 2 Al (s) + 6 HN O 1 (aq) à 2 Al(N O 1 ) 1 (aq) + 3 H $ (g) Hydrogen Displacement 13 Sn (s) + 2 AgN O 1 (aq) à Sn(N O 1 ) $ (aq) + 2 Ag (s) Metal displacement 14 Cl 2 (g) + 2 KI (aq) à 2 KCl (aq) + I 2 (s) Halogen displacement See text, last half of section 4.4 for all of the above The three forms used to write aqueous ionic precipitation reactions (metathesis, or double replacement reactions) discussed in your text, Section 4.2, are also applicable to similar single replacement reactions. For example, the equation shown in Eq. 13: Sn (s) + 2 AgN O 1 (aq) à Sn(N O 1 ) $ (aq) + 2 Ag (s) This is the molecular form of the equation, because the ionic species are written with the cations and anions grouped in single neutral species, as an ionic analog to a molecule. The complete ionic equation shows the individual ions which are the physical species in the solution, Eq. 13a: Sn (s) + 2 Ag & (aq) + 2 N O 1 " (aq) à Sn $& (aq) + 2 N O 1 " (aq) + 2 Ag (s) Ions that appear on both sides of the equation are not directly involved in the reaction and are called spectator ions . To highlight the essentials of the reaction, spectator ions can be "cancelled out", just as in an algebraic equation. The 2 N O 1 " (aq) on both sides of the equation are omitted as undergoing no change, and hence not involved in the reaction, as shown in Eq. 13b : Sn (s) + 2 Ag & (aq) à Sn $& (aq) + 2 Ag (s) This is the net ionic equation for the reaction. The nitrate ions are just a non-reactive vehicle for delivering the Ag & ion. Any soluble salt of Ag & reacting with metallic tin would have the same net ionic equation. For example, the molecular, full ionic, and net ionic equations of metallic tin + aqueous silver acetate are: Molecular Sn (s) + 2 AgC H 1 C O $ (aq) à Sn(C H 1 C O $ ) $ (aq) + 2 Ag (s) Full ionic Sn (s) + 2 Ag & (aq) + 2 C H 1 C O $ " (aq) à Sn &$ (aq) + 2 C H 1 C O $ " (aq) + 2 Ag (s) Net ionic Sn (s) + 2 Ag & (aq) à Sn $& (aq) + 2 Ag (s) Note that the net ionic equation highlights the fact that this is also a redox reaction , where the Sn is oxidized to Sn &$ and the Ag & is reduced to Ag metal. Double-Displacement Reactions: AB + CD à AD + CB, where two or more different substances exchange atoms or ions to form new compounds, usually either a gas, as in a gas formation reaction , a stable or only slightly dissociated molecular compound such as H $ O, as in an

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 6 Overview of the Procedure In this experiment, you will perform a series of experiments, recording the appearance of the reagents before mixing, then observing and recording the signs of reaction (color and/or texture change, creation of a product in. a new phase (ex. gas formation or solid precipitation), evolution of heat, etc. Using the classification scheme of Combination, Decomposition, Single Displacement, and Double Displacement reactions and the specific examples given in Eq. 1- 17, you will find a similar reaction and use the pattern to predict the nature of the product you observed. For example, suppose you burned strontium in air, observing the silvery grey metal form a white powdery substance. Eq. 1-3 indicate the pattern: metals + chalcogenides (Group VIA here, O $ and S * ) yield metallic oxides and sulfides, respectively. Therefore, it is highly likely that the product is SrO, you can classify it as a combination reaction, and you can write the equation, Sr (s) + O $ (g) à 2 SrO (s). For some reactions you may need to refer to Table 2, using the differing physical properties of possible products to predict the actual product of your reaction. For precipitation reactions, use Table 1 to predict the precipitate, and follow the example to write the molecular, full ionic, and net ionic reaction equations for your particular reaction. Table 2: Properties of Some Com pounds Name Chemical Formula Property ammonia N H 1 (g) Pungent odor copper(I) oxide Cu $ O (s) Red solid copper(II) oxide CuO (s) Black solid iron(II) sulfide FeS (s) Black-brown solid iron(III) sulfide Fe $ S 1 (s) Yellow-green solid Experimental Procedure: WEAR YOUR GOGGLES AT ALL TIMES! −5 pt or −10 pt safety penalty HAZARDS : Mg and the gaseous product of the reaction with acid are flammable. Pb (O 1 ) $ is toxic, irritant and oxidant. NaOH and HCl are toxic and corrosive. Heating (NH 3 ) $ C O 1 liberates toxic, corrosive, and irritating fumes.

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