Ionic equation - shows the ions present - illustrates a reaction OR a process like dissolving (physical change)

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Arline Jacobs
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1 Chapter 4: Table 4.8 Soluble dissolves in (or other solvent, if specified) Insoluble doesn t dissolve in (or other solvent, if specified) NaCl, an ionic compound, dissolves in. Na + and Cl - ions are no longer tightly packed together The ions dissociate in solution: NaCl (s) Na + (aq) + Cl - (aq) (s) solid (aq) in solution in (l) liquid (g) gas Formula unit equation reaction equations in chapter 3 - Everything is written as compounds or elements - All species are neutral - illustrates a reaction Ionic equation - shows the ions present - illustrates a reaction OR a process like dissolving (physical change) 1

2 Na 2 SO 4(s) 2Na + (aq) + SO 4 2- (aq) Al 2 (CO 3 ) 3(s) 2Al 3+ (aq) + 3CO 3 2- (aq) Salt ionic compound that contains ions other than H+ or OH- acid produces H+ when dissolved in HCl (g) H + (aq) + Cl - (aq) H 2 SO 4(l) H + - (aq)+ HSO 4 (aq) 2H + 2- (aq)+ SO 4 (aq) Polyprotic acid gives up more than one H + in solution. Ex. H 3 PO 4, H 2 CO 3. Strong acid separates completely in solution (Table 4.5) Ex. HCl, H 2 SO 4, HNO 3 Weak acid separates partly in solution (Table 4.6) Ex. CH 3 COOH, H 2 CO 3 CH 3 COOH (l)? H + (aq) + CH 3 COO - (aq) 2

3 H 2 CO 3(s)? H + (aq)+ HCO 3 - (aq)? 2H + (aq)+ CO 3 2- (aq) Base produces OH - when dissolved in NaOH (s) Na + (aq) + OH - (aq) Strong base separates completely when dissolved (Table 4.7) ex. NaOH, KOH insoluble base doesn t dissolve or barely dissolves in water. Most metal hydroxides (other than those listed in Table 4.7) are insoluble ex. AgOH, Zn(OH) 2 weak base molecular species that partially forms OH - when reacted with. ex. ammonia NH 3 (l) + (l)? NH 4 + (aq) + OH - (aq) neutralization reaction when an acid and base react with each other to form and a salt NaOH (aq) + HCl (aq) NaCl (aq) + (l) Na + (aq) + OH - (aq) + H + (aq) + Cl - (aq) Na + (aq) + Cl - (aq) + (l) Consider this reaction: 3

4 Na 2 SO 4 (aq) + BaCl 2 (aq) BaSO 4 (s) + 2NaCl (aq) Can tell that BaSO 4 is insoluble due to the fact that it forms a solid (s) in water. Precipitation reaction one or more insoluble products are formed. Precipitation reactions and neutralization reactions are special cases of a larger kind of reaction: metathesis reaction ionic compounds reacting to change partners combination reaction more things combine to form less things smaller pieces become bigger pieces ex. Mg + F 2 MgF 2 ex. CaO + CO 2 CaCO 3 4 things P 4 + 3O 2 P 4 O 6 1 thing 6 things P 4 + 5O 2 P 4 O 10 1 thing 4 things 2NaCl + + SiO 2 2HCl + Na 2 SiO 3 2 things 4

5 decomposition reaction less things form more things, or breaking bigger pieces into smaller pieces most important example of decomposition, all combustion reactions: C 3 H 8 + 5O 2 3CO Bigger (11 atoms) smaller (3 atoms) 6 molecules total 7 molecules total decomposition reactions most combustion reactions are decomposition reactions 27 things 2C 8 H O 2 16CO things 26 atoms 5 atoms 3 atoms in one piece in one piece in one piece 9 things 4NH 3 + 5O 2 4NO things 5

6 consider the following reaction: Ba(OH) 2 (aq) + 2HNO 3 (aq) Ba(NO 3 ) 2 (aq) + 2 (l) what volume of 0.246M HNO 3 solution is required to react completely with 38.6 ml of M Ba(OH) 2? Before we were going from grams grams Now we are going from ml ml We know molarity 38.6 ml Ba(OH) 2 solution Mole ratio moles Ba(OH) 2 molarity moles?ml HNO 3 HNO 3 solution 38.6 ml Ba(OH) 2 x mol Ba(OH) 2 2 moles HNO ml HNO x x ml Ba(OH) 2 1 mol Ba(OH) mol HNO 3 molarity Mole ratio molarity = 16.2 ml HNO M = moles = 1 L M = moles = 1 L moles 1000 ml moles 1000 ml 6

7 Consider the following reaction: Strong base Strong acid salt water Ba(OH) 2 (aq) + 2HNO 3 (aq) Ba(NO 3 ) 2 (aq) + 2 (l) What kind of reaction is this? Metathesis, neutralization What is the total ionic equation? Ba 2+ (aq) + 2OH - (aq) + 2H + (aq) + 2NO 3 - (aq) Ba 2+ (aq) + 2NO3 - (aq) + 2H2 O (l) Net ionic equation (the reason the reaction goes ) 2OH - (aq) + 2H + (aq) OH - (aq) + H + (aq) 2 (l) (l) Spectator ions ions that do not participate in the reaction no change Another example: Ca(NO 3 ) 2 (aq) + K 2 CO 3 (aq) solid CaCO 3 (s) + 2 KNO 3 (aq) What kind of reaction is this? Metathesis, precipitation Total ionic equation: Ca 2+ (aq) + 2NO 3 - (aq) + 2K + (aq) + CO3 2- (aq) CaCO3 (s) + 2K + (aq) + 2NO 3 - (aq) Spectator ions 7

8 Net ion ic equation: Ca 2+ (aq) + CO 3 2- (aq) CaCO3 (s) For weak acid w/ strong base: Weak acid Strong base salt water H 3 PO 4 (aq) + 3NaOH (aq) Na 3 PO 4 (aq) + 3 (l) Total ionic equation: H 3 PO 4 (aq) + 3Na + (aq) + 3OH - (aq) 3Na + (aq) + PO 4 3- (aq) + 3H2 O (l) Net ionic equation 3OH - (aq) + H 3 PO 4 (aq) Insoluble base w/strong acid: base Fe(OH) 3 (s) + 3H 2 SO 4 (aq) PO 4 3- (aq) + 3H2 O (l) 3Fe 2 (SO 4 ) 3 (aq) + 6 (l) (aq) (l) Net ionic equation: 2Fe(OH) 3 (s) + 6H + (aq) 6 (l) + 2Fe 3+ (aq) or Fe(OH) 3 (s) + 3H + (aq) 3 (l) + Fe 3+ (aq) 8

9 Understanding chemical formulas Consider the Periodic Table Elements are arranged in rows (periods) of increasing atomic # Elements are arranged in columns (groups) which describe their chemical behavior Elements in blue (on left, most elements) are metals Form cations (usually) Conduct electricity Can be shaped or drawn into wire Shiny Mostly solids Elements in yellow (on right, fewer) are nonmetals (main group) Form anions when combined with metals (usually) Form covalent molecules when combined with each other Poor electrical conductors Not shiny Not easily shaped Solids, liquids, & gases Elements in green (form staircase ) are called metalloids Properties are combination of metals & nonmetals Semiconductors The groups of elements (vertical columns) are particularly useful because they allow us to make generalizations about the elements & their physical/chemical behavior 9

10 For ionic compounds Group IA Li Cs alkali metals form 1+ cations with nonmetals Group IIA Be Ba alkaline earth metals form 2+ cations with nonmetals Group VIIA F I halogens form 1- anions with metals Group VIIIA He Xe noble gases Inert do not react, charge 0 With other groups, the rules are not followed as strictly (encompass some metalloids or metals/nonmetals in the same group): Group IIIA Al In (Tl) Generally form 3+ cations with nonmetals (B is metalloid) Group VA N As (Sb) pnictogens Generally form 3- anions with metals (Bi is metal) Group VIA O Te chalcogens Generally form 2- anions with metals (Po is metal) Group IVA C Pb Often form 4+ cations with nonmetals Often form 4- anions with metals Transition metals variable (2+ common) ex. BeF 2 Be 2+ 2(F-) ex. Cs 2 O 2(Cs+) O 2- ex. AlN Al 3+ N 3-10

11 electron negatively charged particle atoms gain electron atoms lose electron negative charge positive charge atoms gain/lose electrons to resemble noble gases noble gases are very stable charge affects chemical behavior consider the following reaction: 2Na (s) + Cl 2 (g) 2NaCl (s) ionic compound electron transfer (ions formed) oxidation-reduction reaction (redox) from elements we say these atoms have charge but what about the following reaction?: 2H 2 (g) + O 2 (g) 2 (l) covalent compound electron sharing (bonds formed) oxidation-reduction reaction (redox) from elements we say these atoms have formal charge oxidation numbers charges (ions in ionic compound) formal charges (atoms in molecules) 11

12 rules for determining oxidation #s in ionic & covalent compounds: 1. element = zero 2. charge on ion = oxidation # 3. compound = zero 4. (skip for now) 5. F = -1 (except as element) ex. NaF ex. ClF 6. H = +1 with nonmetals (& metalloids) ex. H = -1 with metals ex. NaH 7. O = -2 3 exceptions peroxides O = -1 ( 2 ) superoxides O = -1/2 (KO 2 ) with F ex. OF 2 O = use periodic table (group) to help predict oxidation #. Ex. SO 2 O = 2-2(2-) = 4- S must be 4+ Ex. N 2 O 4 O = 2-4(2-) = 8-8-/2 = 4- N must be Atom closest to F is the negative one. Ex. BCl 3 B = 3+ Cl = 1- Ex. SeCl 2 Cl = 1-2(1-) = 2- Se must be charge of polyatomic ion = sum of formal charges ex. PO 4 3- O = -2, 4(-2) = 8- (8-) (3-) = 5- P must be 5+ 12

13 Naming compounds - binary ionic (metals & nonmetals) o anion ends in ide sodium chloride sodium hydride aluminum nitride boride, carbide, phosphide, telluride, etc. o cation no change in name unless more than on oxidation state is possible iron (II) chloride (ferrous) iron (III) chloride (ferric) - binary covalent (nonmetals & nonmetals) o use prefixes to give elemental proportions di (2) tetra (4) tri (3) penta (5) etc. o in many compounds, 2 nd element will end in ide oxygen compounds sulfur dioxide dinitrogen tetroxide carbon dioxide some sulfur, halogen compounds hydrogen sulfide carbon disulfide boron trichloride 13

14 - binary acids H + more electronegative nonmetal o HCl (g) hydrogen chloride HCl (g) + HCl (aq) hydrochloric acid - ternary acids H, O, nonmetal (memorize, p. 146?) o carbonic acid (H 2 CO 3 ) o boric acid (H 3 BO 3 ) o nitric acid (HNO 3 ) o silicic acid (H 4 SiO 4 ) o phosphoric acid (H 3 PO 4 ) o sulfuric acid (H 2 SO 4 ) o etc o what is oxidation state of S in H 2 SO 4? O is 2- H is 1+ 2(1+) H 2 SO 4 4(2-) 2 + x -8 = 0 x = 6+ o what is oxidation state of P in H 3 PO 4? O is 2- H is 1+ 3(1+) H 3 PO 4 4(2-) 3 + x -8 = 0 x = 5+ o for ternary acids, oxidation state of nonmetal can vary (HClO 4, HClO 3, HClO 2, HClO) name depends on this oxidation state 14

15 per ic (highest oxidation state) HClO 4 = perchloric acid Cl7+ ic (next highest) HClO 3 = chloric acid ous HClO 2 = chlorous acid hypo ous (lowest) HClO = hypochlorous acid Cl5+ Cl3+ Cl1+ Most acids use ic and ous Phosphoric, phosphorous H 3 PO 4, H 3 PO 3 Sulfuric, sulfurous H 2 SO 4, H 2 SO 3 - ternary salts o cation goes first o anion (derived from acid) goes second perbromic acid HBrO 4 H+ + BrO - 4 perbromate ion bromic acid HBrO 3 H+ + BrO - 3 bromate ion bromous acid HBrO 2 H+ + BrO - 2 bromite ion hypobromous acid HBrO H+ + BrO - hypobromite ion ex. Sodium bromate NaBrO 3 2- sulfate SO 4 3- phosphate PO 4 ex. Calcium sulfite CaSO 3 2- sulfite SO 3 3- phosphite PO 3 15

16 - acid salts: salts that still have a proton (or protons) o NaHSO 4 sodium hydrogen sulfate (sodium bisulfate) o NaH 2 PO 4 sodium dihydrogen phosphate o NaHCO 3 sodium bicarbonate HSO 4 - bisulfate ion HCO 3 - bicarbonate ion Table 4-11 a bigger list of ions to memorize New ions like Cyanide (CN-) chromate (CrO 4 - ) 16

Look at the negative ion

Look at the negative ion Major classes of compounds Acids o Have one or more H + ion o Ex: HCl HNO 3 H 2 SO 4 Bases o Have one or more OH - ion o Ex: NaOH Ca(OH) 2 NH 4 OH Oxides o Contain one or more O ion o Ex: CaO Na 2 O (NH