Chemical Equations Part 1

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1 Chemical Equations Part 1 A Directed Learning Activity for Hartnell College Chemistry 1 Funded by the Title V STEM Grant #P031S through Hartnell College For information contact lyee@hartnell.edu Start

2 Student Learning Objectives This tutorial will help you to: 1. Predict products of single and doublereplacement reactions 2. Generate formula, total ionic and net ionic equations using solubility and acid strength information Next

3 Getting Started This set of Power Point slides will lead you through a series of short lessons and quizzes on the topics covered by this Directed Learning Activity tutorial. Move through the slideshow at your own pace. There are several hyperlinks you can click on to take you to additional information, take quizzes, get answers to quizzes, and to skip to other lessons. You can end this slide show at any time by hitting the ESC key on your computer keyboard. Next

4 Table of Topics What You Should Know Classes of Chemical Reactions Single-replacement Reactions Double-replacement Reactions Next Slide

5 What You Should Know Write correct chemical formulas for elements, ions and compounds Balance chemical formula equations Know the difference between strong and weak acids and bases in solution Next Slide

6 Classes of Chemical Reactions A Quick Overview of Synthesis, Decomposition, Single and Double-replacement Reactions Next Slide

7 The Four Major Classes of Chemical Reactions There are many different types of chemical reactions, but they can be broken down into these major categories: Synthesis (Combination) Reactions Decomposition Reactions Single-Replacement Reactions Double-Replacement Reactions The next few slides will explain the general characteristics of each category Next Slide

8 Synthesis (Combination)Reactions Synthesis reactions can be written in symbols as: A + B C Where A and B can be either elements or compounds and C is a new compound. There are three kinds of synthesis reactions: 1. Elements combine to form a compound 2. An element and a compound combine 3. Two compounds combine Next Slide

9 Decomposition Reactions Decomposition reactions can be written in symbols as AA A + B Where AB is a compound, while A and B are elements or simpler compounds. There are three kinds of decomposition reactions: 1. Two (or more) elements are formed 2. Elements and compounds form 3. Two (or more) compounds form Next Slide

10 Single-replacement Reactions Single-replacement reactions can be symbolized as A + BB AA + B Where A and B are two elements and BC and AC are two compounds. There are three basic kinds of singlereplacement reactions: 1. A metal replaces another metal 2. A metal replaces H to form H 2 (g) 3. A nonmetal replaces another nonmetal Next Slide

11 Double-replacement Reactions Double-replacement reactions, also called exchange reactions, may be symbolized: AA + CC AA + BB Where AB and CD are the original compounds and AD and BC are new compounds formed when the original compounds exchange ions or atoms. There are three kinds of double-replacement reactions: 1. Reactions in solution that form a precipitate (an insoluble solid) 2. Reactions that form a gas 3. Reactions that form water (neutralization reactions) Next Slide

12 Details of Singlereplacement Reactions A + BB AA + B Next Slide

13 Example: A Metal Replaces Another Metal in a Compound CC s + 2 AAAA 3 aa CC NN 3 2 aa + 2 AA (s) In this case, solid Cu metal reaction with an aqueous solution of AgNO 3. The Cu and Ag are exchanged and Cu(NO 3 ) 2 is formed in solution while solid Ag metal is formed. Next Slide

14 Example: A Metal Replaces H to Form H 2 (g) MM s + 2 HHH aa MMMM 2 aa + H 2 (g) In this example, solid Mg metal reacts with HCl in solution. MgCl 2 is the product formed in solution, while H 2 gas is released. Note: in balancing this type of equation, remember that hydrogen is one of the diatomic molecular elements. Also, the most reactive metals (Group 1A and 2A) can undergo this type of reaction with water to form hydrogen gas. It is important to remember that this type of reaction often requires a strong acid, depending on the reactivity of the metal. Next Slide

15 Example: A Nonmetal Replaces Another Nonmetal CC 2 aa + 2 NNN aa 2 NNNN aa + I 2 aa In this case a halogen (Group 7A) replaces another halogen in a compound. Note: as with hydrogen, halogens are diatomic molecular elements. Next Slide

16 Quiz Questions ZZ s + CCCC 4 aa? +? CC s + H 2 SS 4 aa? +? CC 2 aa + CCCC 2 aa? +? Answers to Quiz Questions

17 Answers to Quiz Questions ZZ s + CCCC 4 aa ZZZZ 4 aa + CC (s) CC s + H 2 SS 4 aa CCCC 4 aa + H 2 (g) CC 2 aa + CCCC 2 aa CCCC 2 aa + BB 2 (aa) Review this lesson Next lesson

18 Double-replacement Reactions AA + CC AA + BB Next slide

19 Example: Reactions in Solution that Form a Precipitate AAAA 3 aa + NNNN aa NNNN 3 aa + AAAA (s) A precipitate is a solid that forms in solution. In this example, the two reactants are both soluble in water. One of the products, NaNO 3, is also soluble in water. The other product, AgCL, forms a solid precipitate. Note: there are cases when both products will form a precipitate. Next Slide

20 Example: Reactions that Form a Gas NNNNN 3 aa + HHH (aa) NNNN aa + H 2 CC 3 (aa) NNNN aa + H 2 O l + CC 2 (g) In this reaction, two aqueous species eventually produce another aqueous species and a gas. Note: H 2 CO 3, one of the products of the initial reaction, rapidly decomposes to create the gas CO 2. Typical gases that can be produced in this kind of reaction include H 2 S. Note that this type of reaction may require a strong acid. Next Slide

21 Example: Reactions that Form Water HHH 3 aa + NNNN aa NNNN 3 aa + H 2 O(l) When an acid and a base are the reactants, this type of reaction is referred to as a neutralization reaction. The aqueous product is referred to as a salt. The salt has the cation from the base and the anion from the acid. Metal oxides can also react with acids to form water as a product. Next Slide

22 Quiz Questions CC NN 3 2 aa + NN 2 CC 3 aa? +? NN 2 S aa + 2 HHH aa? +? BBB s + 2 HHH 3 aa? +? Check answers

23 Answers to Quiz Questions CC NN 3 2 aa + NN 2 CC 3 aa 2 NNNN 3 aa + CCCC 3 (s) NN 2 S aa + 2 HHH aa 2 NNNN aa + H 2 S(g) BBB s + 2 HHH 3 aa BB NN 3 2 aa + H 2 O (l) Review lesson Next lesson

24 Net Ionic Equations Getting Rid of the Spectators Next slide

25 Representing Reactions When a reaction occurs in aqueous solution, we can write the formula equation, which uses the neutral formulas or symbols for the reactants and products. These are the kinds of equations you have already practiced writing. In certain instances, there are other ways of representing the reaction. The total ionic equation (TIE) separates all the neutral compounds into the ionic species they form in solution. The net ionic equation removes those ions from the equation that do not result in creating a new product. Those ions are called spectator ions, since they don t actually participate in the formation of a new product. Next slide

26 Example: Precipitation Let s use a reaction you have already seen. CC NN 3 2 aa + NN 2 CC 3 aa 2 NNNN 3 aa + CCCC 3 (s) This would be the formula equation. Next slide

27 If we now break down everything that is soluble into ions and rewrite the equation, we obtain the total ionic equation: Ca 2+ (aq) + 2 NO 3- (aq) + 2 Na + (aq) + CO 3 2- (aq) CaCO 3 (s) + 2 Na + (aq) + 2 NO 3- (aq) Inspecting this equation, we see that there are several ions that appear on both sides of the equation. These are the spectator ions. If we remove these, we obtain the net ionic equation: Ca 2+ (aq) + 2 NO 3- (aq) + 2 Na + (aq) + CO 3 2- (aq) CaCO 3 (s) + 2 Na + (aq) + 2 NO 3- (aq) or Ca 2+ (aq) + CO 3 2- (aq) CaCO 3 (s) Next slide

28 We can do similar procedures to the formula equations for the reactions that form gases and for neutralization of acids and bases. What if you are only given the starting materials and have to predict the products of the formula equation before you generate the net ionic equation? Then, you will have a use a table of solubilities like to the one on the next slide. There is probably one similar to it in your lecture text. You also need to know if the acids and bases are weak or strong. Remember that weak acids and bases do not completely dissociate and will be molecular species in solution. There is also an example table of strong acid and base on another slide. Solubility Table

29 Anions Cations C 2 H 3 O - 2 AsO - 4 Br - CO 2-3 Cl - CrO 2-4 OH - I - NO - 3 C 2 O 2-4 O 2- PO 3-4 SO 2-4 S 2- SO 2-3 Al 3+ aq I aq - aq - I aq aq - I I aq d - NH + 4 aq aq aq aq aq aq aq aq aq aq - aq aq aq aq Ba 2+ aq I aq I aq I sl. aq aq aq I sl. aq I I d I Bi 3+ - sl. aq d I d - I I aq I I sl. aq d I - Ca 2+ aq I aq I aq aq I aq aq I I I I d I Co 2+ aq I aq I aq I I aq aq I I I aq I I Cu 2+ aq I aq I aq I I - aq I I I aq I - Fe 2+ aq I aq sl. aq aq - I aq aq I I I aq I sl. aq Fe 3+ I I aq I aq I I - aq aq I I aq I - Pb 2+ aq I I I I I I I aq I I I I I I Mg 2+ aq d aq I aq aq I aq aq I I I aq d sl. aq Hg 2+ 2 sl. aq I I I I sl. aq - I aq I I I I I - Hg 2+ aq I I I aq sl. aq I I aq I I I d I - Ni 2+ aq I aq I aq I I aq aq I I I aq I I K + aq aq aq aq aq aq aq aq aq aq aq aq aq aq aq Ag + sl. aq I I I I I - I aq I I I I I I Na + aq aq aq aq aq aq aq aq aq aq aq aq aq aq aq Sr 2+ aq - aq I aq I aq aq aq - - I I I - Zn 2+ aq I aq I aq I I aq aq I I I aq I I N e x t

30 Examples of Strong Acids & Bases Strong acids in aqueous solutions: HClO4, H 2 SO4, HI, HBr, HCl, HNO 3 Strong bases in aqueous solutions: LiOH, KOH, NaOH, Ca(OH) 2 Remember that strong refers to species that dissociate (almost) completely to ions in water. Next slide

31 Quiz Questions Write the net ionic equations for these reactions: K 2 SO 4 (aq) + BaBr 2 (aq)? +? Na 2 CO 3 (aq) + 2 HCl (aq)? +? +? Ca(OH) 2 (aq) + 2 HCl (aq)? + H 2 O (l) Next slide

32 Answers to Questions K 2 SO 4 (aq) + BaBr 2 (aq) 2 KBr (aq) + BaSO 4 (s) Ba 2+ (aq) + SO 4 2- (aq) BaSO 4 (s) Comment: look at solubility of the possible products to see that one of the products is solid. Delete the spectator ions to yield the net ionic equation. Na 2 CO 3 (aq) + 2 HCl (aq) 2 NaCl (aq) + H 2 O (l) + CO 2 (g) 2 H + (aq) + CO 2-3 (aq) H 2 O (l) + CO 2 (g) Comment: Refer to gas generation example. Delete the spectator ions to generate the net ionic equation. Next slide

33 Ca(OH) 2 (aq) + 2 HCl (aq) 2 H + (aq) + 2 OH - (aq) 2 H 2 O (l) CaCl 2 (aq) + 2 H 2 O (l) Comment: This net ionic equation is common to all acid-base neutralization reactions Review lesson Next slide

34 Congratulations! You have successfully completed this Directed Learning Activity tutorial. We hope that this has helped you to better understand this topic. Click here to end. Click here to repeat this activity.

35 Information This document has been prepared in compliance with US & International Copyright Laws 2011 Hartnell College Funded by the Title V STEM Grant #P031S through Hartnell College Hit ESC key to end this slide show

3a. The acid and base react to form a salt solution of ammonium propionate. CaCO s + 2 HC H O aq CO g + H O l + Ca ( aq ) + 2 C H O ( aq)

3a. The acid and base react to form a salt solution of ammonium propionate. CaCO s + 2 HC H O aq CO g + H O l + Ca ( aq ) + 2 C H O ( aq) Chapter 5 Answers Practice Examples 1a. 0.50 M Cl 1b. (a) 7.9 10-5 M F - ; (b).1 kg CaF a. (a) Al ( aq ) OH ( aq ) Al ( OH) ( s) (b) No reaction occurs. (c) Pb ( aq ) I ( aq ) PbI ( s) b. (a) Al ( aq )