Topic: Chemical Equations

Transcription

1 Chemical Equations Lesson Objectives List evidence that suggests that a chemical reaction has occurred and evidence that proves that a chemical reaction has occurred. Describe a chemical reaction by using a word equation and a formula equation. Interpret notations in formula equations, such as those relating to states of matter or reaction conditions. Lesson objectives Teachers' notes Nov 4 10:26 AM Subject: General Chemistry (CP) Topic: Chemical Equations Grade(s): 11,12 Prior knowledge: molar conversion, writing chemical formulas Cross curricular link(s): Balancing algebraic equations; Lesson notes: Type text here Lesson objectives Teachers' notes Nov 4 10:26 AM 1

2 Evidence of a chemical reaction includes the following: 1. Emission of heat and light 2. change in color 3. Formation of a precipitate 4. Release of a gas 5. Temperature change Apr 2 4:23 PM Writing and Balancing Chemical Equations Chapter 8 Apr 2 4:19 PM 2

3 May 5 9:33 AM Chemical Reaction Na2O + H2O 2Na(OH) reactants yield products arrow A chemical reaction is the process by which one or more substances change into one or more new substances. Reactants are the original substances in a chemical reaction. Products are the substances that are created in a chemical reaction. Apr 2 4:23 PM 3

4 Characteristics of Chemical Equations Equation that represents a reaction (RXN) 1. The equation must represent the known facts All reactants and products must be identified by either experiment in the lab or from resources that report the results Apr 2 4:23 PM Characteristics of Chemical Equations, cont'd 2. The equation must contain the correct formulas This will include subscripts and correct chemical symbols following the procedures and rules in chapter 7. Mar 31 7:51 AM 4

5 Characteristics of Chemical Equations, con't 3. The law of conservation of mass must be obeyed This will involve balancing the number of atoms of each element on either side of the equation through the use of coefficients 4. All physical states must be identified Mar 31 7:51 AM Word and Word Equations The first step: Identify the facts What are the elements and compounds involved? What are the products? What are the reactants? What phase are they in? Are there any catalysts? Apr 13 10:38 AM 5

6 Example: Describe, with words, combustion of methane gas with oxygen gas The combustion of methane gas produces water vapor and carbon dioxide gas Our word equation is: methane + oxygen carbon dioxide ( ) + water vapor () his is read: methane and oxygen react to yield carbon dioxide gas and water vapor Mar 2 12:13 PM The next step is to replace the words with the correctly written formulas Our word equation is: methane (g) + oxygen (g) carbon dioxide ( ) + water vapor () We know: methane: CH 4 Oxygen: O 2 Carbon Dioxide: CO 2 Water: H 2O CH 4 (g) +O 2 (g) CO 2 (g) + H 2 O ( ) Mar 2 12:16 PM 6

7 CH 4 (g) +O not completely 2 (g) CO 2 (g) + H 2 O(g) done!! it isn't balanced! We must obey the law of conservation of mass which states: CH 4 (g) +O 2 (g) CO 2 (g) + H 2 O(g) Mar 2 12:20 PM What do the coefficients in a chemical equation mean?. Ratio of molecules, atoms, or moles of the substances in a reaction Mar 2 1:33 PM 7

8 Balancing Chemical Equations The law of conservation of mass means that the number of atoms for each element on the left side of the equation (reactants) equal the number on the right (products). lets take a look at this process... Mar 31 7:55 AM Here is a description of how hydrogen and oxygen make water: Hydrogen (gas) + Oxygen (gas) gives us water vapor (gas) H O + O first problem: we know that hydrogen and oxygen are molecules... H H Mar 31 9:25 AM 8

9 diatomic, so we adjust the equation: H O O H H next problem: count up the Number of atoms on each side of the arrow: Mar 31 9:29 AM H O O H H H: 2 O: 2 oxygen is not balanced BUT H: 2 O: 1 once the correct formulas are written, changing the subscript changes the substance, so we can't do that (H 2O 2 is not water vapor, it is hydrogen peroxide!) Mar 31 9:30 AM 9

10 More Practice writing and balancing equations Solid Lithium hydroxide is reacted with sulfuric acid to give the solid ionic salt lithium sulfate, in water. 1. Write the word equation: Lithium hydroxide(s) + sulfuric acid(aq) Lithium sulfate precipitate and water 2. Write the correct formulas for each compound. LiOH(s) +H 2SO 4(aq) Li 2SO 4( ) + H 2O (l) 3. Balance the atoms LiOH(s) +H 2SO 4(aq) Li 2SO 4( ) + H 2O (l) Mar 20 1:39 PM May 8 8:08 AM 10

11 May 8 8:18 AM May 8 8:27 AM 11

12 More Practice writing and balancing equations In a precipitation reaction, sodium hydroxide solution is mixed with iron(ii) chloride solution. Sodium Chloride solution and insoluble iron(ii) hydroxide are produced. Write a balanced chemical equation including the state symbols. 1. Word equation: Sodium hydroxide(aq) + iron (II) chloride (aq) sodium chloride(aq) + iron(ii) hydroxide (s). 2. correct formulas: NaOH (aq) + FeCl 2 (aq) NaCl (aq) + Fe(OH) 2 (s) 3. balance Mar 20 1:51 PM hint if the same polyatomic ion is on both sides, balance as a unit, not as individual ions NaOH (aq) + FeCl 2(aq) NaCl (aq) + Fe(OH) 2 (s) Na Na OH OH Fe Fe Cl Cl Mar 20 2:01 PM 12

13 Write a balanced chemical equation for Sodium(s) + hydrochloric acid(aq) sodium chloride(aq) + hydrogen(g) Mar 20 2:04 PM 1. Silver nitrate + sulfuric acid > silver sulfate + nitric acid 2. glucose + oxygen > water and carbon dioxide Apr 27 2:54 PM 13

14 3. C 4 H 10 + O 2 H 2 O + CO 2 Butane + oxygen Water + carbon dioxide 4. potassium chlorate potassium chloride + oxygen Apr 27 3:05 PM 5. (NH 4 ) 2 CO 3 NH 3 + CO 2 + H 2 O 6. NH 3 (g) + HCl(aq) NH 4 Cl(aq) Apr 27 3:43 PM 14

15 sodium bromide + phosphoric acid sodium phosphate + hydrobromic acid H 2 SO 4 (aq) + NaOH(aq) Na 2 SO 4 (aq) + H 2 O(l) Apr 27 3:45 PM AgNO 3 (aq) + Mg(s) Ag(s) + Mg(NO 3 ) 2 (aq) HCl(aq) + Na 2 CO 3 (s) NaCl(aq) + CO 2 (g) +H 2 0(l) hydrogen gas + nitrogen gas yields ammonia Apr 27 3:47 PM 15

16 Solid potassium reacts with liquid water yielding potassium hydroxide and hydrogen gas. Mar 20 2:08 PM Apr 27 8:42 AM 16

17 Niagara High School. (2017, April). General Chemistry, Period # [Class handout: Chemistry: Lab Formula of a Hydrate]. Niagara, WI: Author, Unknown. Materials: (handout) May 9 9:40 AM Types ofchemical Reactions Apr 16 4:03 PM 17

18 chemical equations_april 2014_mine.notebook thousands of chemical reactions It is necessary to predict the products of a reaction Apr 16 4:07 PM We will look at 6 basic types of chemical reactions Synthesis Decomposition Single Displacement Double Displacement Acid-Base Combustion + + Apr 16 4:15 PM 18

19 Synthesis Reactions Also known as "Composition Reactions" 2 or more substances combine to form a new compound General form: A + X AX *where A and X may be elements or compounds & *AX is a compound Apr 16 4:30 PM a) elements + oxygen will yield an oxide of the element almost all metals react with oxygen to form metal oxides Group I elements will form oxides of the general formula M 2 O, where M represents a metal from group I ex.1: 4Li +O 2 2Li 2 O Group II elements will form oxides of the general formula: MO, where the M represents a metal from group II. ex. 2: 2Mg + O 2 2MgO Apr 16 10:02 PM 19

20 . Other metals form more than one oxide with oxygen: Iron combined with oxygen can result in iron (II) oxide or on(iii) oxide. 2Fe(s) + O 2 (g) 2FeO (s) (iron (II) oxide) 4Fe (s) + 3O 2 (g) 2Fe 2 O 3 (s) (iron (III) oxide) Apr 16 10:15 PM c. Nonmetals also combine with oxygen to form oxides: Sulfur reacts with oxygen to from sulfur dioxide S 8 (s) + O 2(g) 8SO 2(g) Carbon, when burned in air will form carbon dioxide C (s) + O 2 (g) CO 2(g) If C is burned in a limited amount of oxygen, the poison CO is formed instead Mar 30 3:18 PM 20

21 Synthesis Reactions, cont'd d. Sulfur will react with Group I and II metals to form metal sulfides 16 Rb + S 8 8Rb 2 S 8H 2 + S 8 8H 2 S Apr 16 10:11 PM e. Metals + halogens group I will combine w/ halogens to form ionic compounds of the general formula A + X -> AX AX and II metals: AX 2 Mg + Cl 2 => MgCl 2 potassium and Chlorine will combine to make Potassium chloride 2K + Cl 2 2KCl Apr 16 10:53 PM 21

22 f. Oxides of active metals will combine with water to form metal hydroxides example: CaO + H 2O Ca(OH) 2 other examples: Na 2 O + H 2 O 2Na(OH) Apr 16 10:57 PM Decomposition One compound breaks down into two substances The general equation for decomposition AX A + X Where A and X may be elements or compounds AX is a compound Apr 17 2:13 PM 22

23 1. Decomposition of binary compounds: This is the simplest type of decomposition reactions lectric Pull H 2 + O 2 Pull e when Pull +O Pull 2 g) IN GENERAL, BINARY COMPOUNDS WILL SPLIT INTO TWO ELEMENTS. Feb 13 04:16 ioxide gas Pull es a metal Pull ve a metal Pull etal oxides 5 Pull Feb 13 04:16 23

24 Next: displacement reactions displacement: replace one thing by moving it and replacing with another Apr 23 2:35 PM Single displacement reactions 4 basic categories: Displacement of a metal in a compound by another metal Displacement of hydrogen in water by a metal displacement of hydrogen in an acid by a metal displacement of halogens A + BX AX +B Y + BX BY + X Anions do not displace cations A, B, X, Y are elements; AX, BX, BY are compounds Apr 21 7:30 PM 24

25 Double Displacement AX + BY AY + BX X and Y switch places Note You must start and end with: cation anion / cation anion Apr 23 2:51 PM In double displacement reactions, the ions of 2 compounds switch places a. Formation of a Precipitate When the cations of one reactant combine with the anions of another reactant insoluble or slightly soluble compound is form. 2KI(aq) + Pb(NO3)2(aq) PbI2(s) + 2KNO3(aq) The precipitate forms as a result of the very strong attractive forces between the Pb 2+ cations and the I - anions. Apr 23 2:57 PM 25

26 Formation of a Gas START HERE 3RD PERIOD 5/16 FeS(s) + 2HCl(aq) H2S(g) + FeCl 2(aq) Formation of Water HCl(aq) + NaOH(aq) NaCl(aq) + H2O(l) A.K.A. : Acid Base reaction Apr 27 10:17 AM Combustion reactions In a combustion reaction, a substance combines with oxygen, releasing a large amount of energy in the form of light and heat. example: combustion of hydrogen 2H 2(g) + O 2(g) 2H 2O(g) example: combustion of propane C 3 H 8 (g) + 5O 2 (g) 3CO 2 (g) + 4H 2 O(g) + heat & light In other words, a combustion reaction always gives us water If an organic compound is involved, we will get CO2 Apr 27 12:02 PM 26

27 Apr 27 12:41 PM Is there only one reactant? Summary flow chart: if yes decomposition reaction NO? are the reactants if yes 2 simple elements or 2 simple compounds that combine to make a more complex substance?? synthesis reaction NO? NO? Are the reactants oxygen and a hydrocarbon or oxygen and hydrogen if yes combustion reaction Are the reactants two compounds composed of ions? if yes double displacement NO? Are the reactants one compound and one element NO? You have missed a clue, go back to step one and try again if yes single displacement Apr 27 12:41 PM 27

28 - activity series.notebook Activity series Activity Series of metals Table 3 of Modern Chemistry; page 286 Activity of Metals Activity of Halogens Li F Rb React with cold H 2 O and Cl 2 K acids, replacing hydrogen. Br 2 Ba React with oxygen, I 2 Sr forming oxides Ca Na Mg Al React with steam, but Mn not cold water. React w/ Zn acids, replacing hydrogen. Cr React with oxygen, Fe forming oxides Cd Co Do not react with water. Ni React with acids, Sn replacing hydrogen. Pb react with oxygen, forming oxides H 2 Sb react with oxygen Bi forming oxides Cu Hg Ag fairly unreactive Pt forming oxides Au indirectly Apr 27 1:20 PM May 9 7:35 AM 28

29 May 9 7:35 AM 29

30 Attachments hc608_01_v02fs.htm activity series.notebook HighSchoolChemistryBalancingEquations[1].notebook