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Double Replacement Rxn Chemistry I. 6/11/20142 A closer look at Double Replacement Reactions Instead of FIGHTING (Single Replacement) Double Rep. Are.

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Presentation on theme: "Double Replacement Rxn Chemistry I. 6/11/20142 A closer look at Double Replacement Reactions Instead of FIGHTING (Single Replacement) Double Rep. Are."— Presentation transcript:

1 Double Replacement Rxn Chemistry I

2 6/11/20142 A closer look at Double Replacement Reactions Instead of FIGHTING (Single Replacement) Double Rep. Are all about LOVE Evidence of the DR is either: – A precipitate forming – an acid/base (two ionic) reaction forming covalent water molecules neutralization If neither happens, No Reaction

3 3 Aqueous Solutions Many times, the chemicals we are reacting together are dissolved in water. – Mixtures of a chemical dissolved in water are called aqueous solutions. The chemicals must first be dissolved in water – Compounds separate into free ions.

4 6/11/20144 When some ionic compounds dissolve in water, The anions and cations are separated from each other. Dissociation Because they are more attracted to polar water molecules. NaCl(s) Na + (aq) +Cl - (aq) Ions are FREE to move throughout the solution.

5 5 When compounds containing polyatomic ions dissociate, the polyatomic group stays together as one ion. AgNO 3 (s) Ag + (aq) + NO 3 - (aq)

6 6 Dissociation, Continued Sodium chloride dissociates in water NaCl(s) Na +1 (aq) + Cl -1 (aq) Silver nitrate dissociates in water AgNO 3 (s) Ag +1 (aq) + NO 3 -1 (aq) Na +1 Cl -1 Na Cl Ag +1 NO 3 -1 Ag NO 3

7 7 DR Reactions Occurs if A cation and anion combine to form an insoluble precipitate. If no precipitate forms, then NR (no reaction).

8 8 Why did a precipitate form? Ions in AgCl are more attracted to each other than to the polar water molecules. Fall madly deeply in love, wrap their arms around each other, and drop out of the solution as a solid. AgCl(s)

9 What about the other couple, NaNO3 ? The ions of NaNO 3 are more attracted to the polar water molecules and stay separate (dissociated) Soluble product is shown as (aq) Na + (aq) + NO 3 - (aq) 6/11/20149

10 So, how do you know if a new product is (s) or (aq)? Solubility Rules 6/11/ Gross equation: NaCl(aq) + AgNO 3 (aq) AgCl(s) + NaNO 3 (aq) Net equation: Cl - (aq) + Ag + (aq) AgCl (s)

11 6/11/ Solubility of Ionic Salts General Rules 1. Sodium (Na +1 ), potassium (K +1 ), and ammonium (NH 4 +1 ) compounds are soluble in water. 2. Nitrates (NO 3 -1 ), acetates (C 2 H 3 O 2 -1 ), and chlorates (ClO 3 -1 ) are soluble. 3. Chlorides (Cl -1 ) are soluble except with silver (Ag +1 ), mercury(I) (Hg 2 +2 ), and lead(II) (Pb +2 ). [Lead(II) chloride is soluble in hot water.] 4. Sulfates (SO 4 -2 ) are soluble except with calcium (Ca +2 ), barium (Ba +2 ), strontium (Sr +2 ), and lead(II) (Pb +2 ). 5. Carbonates (CO 3 -2 ), phosphates(PO 4 -3 ), and silicates (SiO 3 -2 ) are insoluble except with sodium (Na +1 ), potassium (K +1 ), and ammonium (NH 4 +1 ). 6. Sulfides (S -2 ) are insoluble except with calcium (Ca +2 ), barium (Ba +2 ), strontium (Sr +2 ), magnesium (Mg +2 ), sodium (Na +1 ), potassium (K +1 ), and ammonium (NH 4 +1 ).

12 12 Solubility Patterns… Generally SolubleGenerally Insoluble Cations: NH 4 +, Li +, Na +, K + Cations: Ag +, Pb 2+, Hg 2+ Anions: Cl -, Br -, I -, NO 3 -, ClO 3 -, C 2 H 3 O 2 - Anions: OH -, S 2-, CO 3 2-, PO 4 3-, CrO 4 2-

13 Determine whether each of the salts is soluble or insoluble: AgBr CaCl 2 Pb(NO 3 ) 2 PbSO 4 CuS Fe 2 (SO 4 ) 3 PbCO 3 NH 4 Cl 6/11/ AgBr insoluble CaCl 2 soluble Pb(NO 3 ) 2 soluble PbSO 4 insoluble CuS insoluble Fe 2 (SO 4 ) 3 soluble PbCO 3 insoluble NH 4 Cl soluble

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15 15 Precipitation Reactions, Continued 2 KI(aq) + Pb(NO 3 ) 2 (aq) 2 KNO 3 (aq) + PbI 2 (s)

16 16 DR Precipitation Reaction 2 KI(aq) + Pb(NO 3 ) 2 (aq) 2 KNO 3 (aq) + PbI 2 (s)

17 17 No Precipitate Formation = No Reaction KI(aq) + NaCl(aq) KCl(aq) + NaI(aq) All ions still present, no reaction.

18 18 Process for Predicting the Products of a Precipitation Reaction 1.Write the formula for the reactants. 2.Exchange ions. (Trade dance partners) (+) ion combines with (-) ion 3.Criss-cross ionic charges of new dance couples to get formulas. (Dont worry about balancing the equation yet.) 4.Use the solubility rules to determine solubility of each product in water. – If product is insoluble or slightly soluble, it will precipitate. Write (s) behind it. – If the product is soluble, write (aq) behind it. – If neither product will precipitate, no reaction. 5. Eliminate the spectator ions (those that are (aq) on both sides) 6. Write a balanced net ionic equation.

19 19 An aqueous Solution of Sodium Carbonate Is Added to an Aqueous Solution of Copper(II) Chloride, a White Solid Forms. 1.Write the formulas of the reactants Na 2 CO 3 (aq) + CuCl 2 (aq) 2.Exchange the ions. Na 2 CO 3 (aq) + CuCl 2 (aq) Na + + Cl - + Cu 2+ + CO Criss-Cross charges and reduce Na 2 CO 3 (aq) + CuCl 2 (aq) NaCl + CuCO 3

20 4. Determine solubility of products NaCl is soluble CuCO3 is insoluble. Na 2 CO 3 (aq) + CuCl 2 (aq) NaCl(aq) + CuCO 3 (s) 5. Na + and Cl - are (aq) on both sides. Spectators. Eliminate. 6.Net ionic equation: CO 3 2- (aq) + Cu 2+ (aq) CuCO 3 (s) 6/11/201420

21 6/11/ Consider: AlCl 3 (aq) + AgNO 3 (aq) Write the dissociation equation of each reactant: AlCl 3 (s) Al +3 (aq) + 3 Cl -1 (aq) Why 3 Cl -1 (aq) and NOT Cl 3 -1 ? AgNO 3 (s) Ag +1 (aq) + NO 3 -1 (aq)

22 6/11/ One of two things can happen: All ions remain free No reaction happens. Two oppositely charged ions are attracted to each other strongly, bond Form a precipitate.

23 6/11/ What are the products (possible new dance couples? Al +3 combines with NO 3 - : Al(NO 3 ) 3 Ag +1 combines with Cl -1 : AgCl Why NOT AlAg? Or NO 3 Cl ? Does one, both, or neither product form a precipitate?

24 6/11/ AgCl insoluble AgCl (s) Al(NO 3 ) 3 soluble Al +3 (aq) + 3NO 3 -1 (aq)

25 6/11/ Gross and Net Equations Al +3 (aq) + 3 Cl -1 (aq) + 3Ag +1 (aq) + 3NO 3 -1 (aq) 3 AgCl (s) + Al +3 ( aq) +3 NO 3 - (aq) Eliminate spectators. Net Ionic equation: Ag + (aq) + Cl _ (aq) AgCl (s)

26 6/11/ Pb(NO 3 ) 2 (aq) + KI (aq) Write the dissociation equations for each salt. Pb +2 (aq) + NO 3- (aq) + K + (aq) + I - (aq) Determine what the products are. PbI 2 and KNO 3

27 6/11/ Pb(NO 3 ) 2 (aq) + KI (aq) Which is the precipitate? PbI 2 is insoluble (forms a precipitate) Gross Equation: Pb +2 (aq) + NO 3- (aq) + K + (aq) + I - (aq) PbI 2 (s) + KNO 3 (aq) Net Ionic Equation: Pb 2+ (aq) + 2 I - (aq) PbI 2 (s)

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29 6/11/ FeBr 2 (aq) + AgNO 3 (aq) Dissociation of reactants? Fe +2 (aq) + 2 Br – 1 (aq) + Ag +1 (aq) + NO 3 -1 (aq) New Dance Couples? Fe (NO 3 ) 2 and AgBr Check table for precipitate Fe(NO 3 ) 2 is soluble or (aq) AgBr is insoluble or (s)

30 6/11/ Fe +2 (aq) + 2 Br – 1 (aq) + Ag +1 (aq) + NO 3 -1 (aq) Fe +2 (aq) + NO 3 -1 (aq) + AgBr (s) Net ionic Equation: Ag +1 (aq) + Br -1 (aq) 2AgBr (s)


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