Beaker A Beaker B Beaker C Beaker D NaCl (aq) AgNO 3(aq) NaCl (aq) + AgNO 3(aq) AgCl (s) + Na 1+ 1

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1 CH 11 T49 MIXING SOLUTIONS 1 You have mastered this topic when you can: 1) define the terms precipitate, spectator ion, suspension, mechanical mixture, solution. 2) write formula equations, complete/total ionic equation and net ionic/precipitation equations for solutions created by mixing two ionic solutions or mixing acid and a base solutions. MIXING IONIC SOLUTIONS I) RECALL that an aqueous solution contains dissolved particles that are spread evenly throughout the solvent water molecules. Dissociation equations are used to describe the dissolving of the solute and the particles that exist within the aqueous solution. A) Consider the soluble salt (ionic compound) lithium sulphide. Because it is soluble its formula units break apart into individual ions in much the same way as the dissociation of sodium chloride illustrated in Figure 8 on page 278 of your text. The dissociation of lithium sulphide in water to form an aqueous solution is described in this dissociation equation: Li 2 S (s) 2Li 1+ + S 1) The single arrow in the above dissociation equation indicates that all of the solid lithium sulphide has dissociated, broken apart, and now exists as the ions indicated on the right hand side of the arrow. Those ions are floating in solution surrounded by the solvent water molecules. In other words, none of the Li 2 S (s) exists as it has all been dissociated and now exists as 2Li 1+ + S. Dissociation of ionic solutes in water is very common and is so very well understood that chemists have come to accept that the compound s formula followed by means the salt has dissolved in water and now exists as ions floating in solution surrounded by the solvent water molecules: i.e. Li 2 S means 2Li 1+ + S. REMEMBER NaCl (s) means the Na 1+ and Cl are bonded to each other and locked in place within the solid crystal lattice while NaCl means Na 1+ + Cl are floating in solution in solution surrounded by the solvent water molecules. Li 3 PO 4(s) means the 3Li 1+ and PO 4 3 are bonded to each other and locked in place within the solid crystal lattice while Li 3 PO 4 means 3Li 1+ + PO 4 3 are floating in solution in solution surrounded by the solvent water molecules. Having a clear understanding of the different meanings of substances formula written as a solid (e.g. NaCl (s) ) or as an aqueous solution (e.g. NaCl ) will be very helpful in understanding what happens when solutions are mixed together. II) When two solutions containing soluble ionic solutes are mixed one must consider all of the possible chemical reactions that can occur between the ions that exist within the newly formed solution. A) Consider the mixing of a sodium chloride solution (NaCl ) and a silver nitrate solution (AgNO 3 ). 1) Because both salts (ionic compounds) are aqueous, each exists as ions surrounded by the solvent water molecules dispersed evenly throughout the solution as illustrated in Beakers A and B of Figure 1 below. Figure 1: Illustration of mixing two ionic solutions. Na 1+ + Cl + Ag 1+ Na1+ + Cl + Ag 1+ Na1+ + NO 3 AgCl (s) Beaker A Beaker B Beaker C Beaker D NaCl AgNO 3 NaCl + AgNO 3 AgCl (s) + Na 1+ a) When the two ionic solutions (Beakers A & B) are mixed together, a new solution consisting of all four ions is created as illustrated in Beaker C. The newly formed solution in Beaker C allows the ions to mix together and interact with each other. If a combination of ions has low solubility as indicated by the Solubility of Ionic Compounds Chart a precipitate (solid compound) will form and sink to the bottom of the beaker which is illustrated in Beaker D.

2 CH 11 T49 MIXING SOLUTIONS 2 B) The process of mixing two ionic solutions as illustrated in Figure 1 on page 1 of these notes is represented by three different kinds of equations: FORMULA EQUATION, COMPLETE/TOTAL IONIC EQUATION and NET IONIC EQUATION. 1) A FORMULA EQUATION is a balanced equation written using the complete formula and state of each reactant solute compound and each predicted/possible product compound formed. a) e.g. The formula equation for the reaction resulting from the mixing of sodium chloride and silver nitrate illustrated in Figure 1 on page 1 of these notes is given here: NaCl + AgNO 3 AgCl (s) + NaNO 3 i) NOTICE that this formula equation is a double replacement reaction (see T19). The formula equation describing the reactions created by mixing two ionic solutions is a double replacement reaction. BE SURE THE FORMULA OF EACH COMPOUND IS WRITTEN CORRECTLY (see T10). ii) RECALL that when the formula of an ionic compound indicates the compound is aqueous (i.e. NaCl ), the compound actually exists as ions (i.e. Na 1+ + Cl ). This information allows chemists to write complete/total ionic equations, which more accurately reflect formula of the solute particles that actually exist in an aqueous solution. 2) A COMPLETE/TOTAL EQUATION is a balanced equation written using the formula and state of each aqueous (soluble) reactant and product compound written as ions and each precipitated (low solubility, solid) product compound formed. a) e.g. The complete/total ionic equation for the reaction resulting from the mixing of sodium chloride and silver nitrate illustrated in Figure 1 on page 1of these notes is given here: Na 1+ + Cl + Ag 1+ + NO 3 AgCl (s) + Na 1+ + NO 3 i) NOTICE that this complete/total ionic equation shows all aqueous (soluble) reactant and product compounds written as ions and the low solubility precipitated product formed written as a complete solid compound. NOTE: A reaction s complete/total ionic equation is used to identify those ions that are involved in a reaction (the ions that form a precipitated solid) and those ions that are not involved in a reaction (do not form a precipitated solid). The ions that are NOT involved in a reaction (do not form a precipitated solid) are called SPECTATOR IONS. They are called spectator ions because they watch the other ions react together in much the same way the spectators at a hockey game watch the players reacting on the ice. Spectator ions are identified by their appearance on both the reactant and product side of the complete/total ionic equation. The spectator ions in the above complete/total ionic equation are Na 1+ + NO 3. 3) A NET IONIC EQUATION is a balanced equation written using the formula of the aqueous (soluble) ions that reactant together to produce the precipitated (solid) product compound formed. a) e.g. The net ionic equation for the reaction resulting from the mixing of sodium chloride and silver nitrate illustrated in Figure 1 on page 1 of these notes is given here: Ag 1+ + Cl AgCl (s) i) NOTICE that this net ionic equation shows only the aqueous reactant ions that react together to form the precipitated (solid) product compound which is written as a complete solid compound. NOTICE that this net ionic equation produces a solid ionic compound that is referred to as a precipitate. Because a precipitate (solid) compound is formed, this type of net ionic equation is also, and often, called a PRECIPITATION EQUATION. 3) Sample Problems 1: Write the formula equation (FE), complete/total ionic equation(c/tie) and the net ions (SI). 1. Aqueous sodium sulphate mixed with aqueous barium sulphide. FE: Na 2 SO 4 + BaS BaSO 4(s) + Na 2 S C/TIE: 2Na 1+ + SO 4 + Ba 2+ + S BaSO 4(s) + 2Na 1+ + S NI/PE: Ba 2+ + SO 4 BaSO 4(s) Na 1+ + S Continued on the next page.

3 CH 11 T49 MIXING SOLUTIONS 3 2. Aqueous aluminum sulphate mixed with aqueous calcium nitrate. FE: Al 2 (SO 4 ) 3 + 3Ca(NO 3 ) 2 3CaSO 4(s) + 2Al(NO 3 ) 3 C/TIE: 2Al SO 4 + 3Ca NO 3 3CaSO 4(s) + 2Al NO 3 NI/PE: Ca 2+ + SO 4 CaSO 4(s) Al 3+ + NO 3 4) Required Practice 1. Write the formula equation (FE), complete/total ionic equation(c/tie) and the net ions (SI). {Answers are on page 4 of these notes.} 1. KCl + AgNO 3 3. Pb(NO 3 ) 2 + Li 2 SO 4 5. NaC 2 H 3 O 2 + AgNO 3 2. MgCl 2 + NaOH 4. K 3 PO 4 + CuCl 2 6. HBr + Cu 2 S MIXING ACID AND BASE SOLUTIONS I) RECALL that an acid is an aqueous molecular compound beginning with hydrogen (i.e. HCl, H 3 PO 4 ) and a base in an aqueous ionic compound ending with OH (i.e. NaOH, Sr(OH) 2 ). When acidic and basic solutions are mixed together a neutralization reaction occurs creating a salt and liquid water as illustrated here: Acid + Base Salt (aq or s) + Water (l) A) The process of mixing acid and base solutions can be illustrated using the same three equations introduced in the section describing the mixing of two ionic solutions: FORMULA EQUATION, COMPLETE/TOTAL IONIC EQUATION and NET IONIC EQUATION. 1) Sample Problems 2: Write the formula equation (FE), complete/total ionic equation(c/tie) and the net ions (SI). 1. An acetic acid solution is mixed with a solution of barium hydroxide. FE: 2HC 2 H 3 O 2 + Ba(OH) 2 Ba(C 2 H 3 O 2 ) 2 + 2H 2 O (l) C/TIE: 2H + + 2C 2 H 3 O 2 + Ba OH Ba C 2 H 3 O 2 + 2H 2 O (l) NIE: H + + OH H 2 O (l) Ba 2+ + C 2 H 3 O 2 NOTICE that when the net ionic equation for this reaction between an acid and base is not a precipitation reaction because a precipitate (solid) is not formed. 2. A solution of sulphuric acid is mixed with aqueous strontium hydroxide. FE: H 2 SO 4 + Sr(OH) 2 SrSO 4(s) + 2H 2 O (l) C/TIE: 2H + + SO 4 + Sr OH SrSO 4(s) + 2H 2 O (l) NI/PE: 2H + + SO 4 + Sr OH SrSO 4(s) + 2H 2 O (l) None NOTICE that when the net ionic equation for this reaction between an acid and base is a precipitation reaction because a precipitate (solid) is formed. In this case the complete/total ionic equation is the same as the net ionic/precipitation equation. 4) Required Practice 2. Write the formula equation (FE), complete/total ionic equation(c/tie) and the net ions (SI). {Answers are on page 4 of these notes.} 1. HCl + LiOH 3. HNO 3 + KOH 5. H 2 CO 3 + Sr(OH) 2 2. H 2 SO 4 + NaOH 4. HC 2 H 3 O 2 + Ba(OH) 2 6. H 3 PO 4 + Mg(OH) 2

4 CH 11 T49 MIXING SOLUTIONS 4 ANSWERS TO THE REQUIRED PRACTICE Required Practice 1 from page 3 1. FE: KCl + AgNO 3 KNO 3 + AgCl (s) C/TIE: K 1+ + Cl + Ag 1+ K 1+ + AgCl (s) NI/PE: Ag 1+ + Cl AgCl (s) K FE: MgCl 2 + 2NaOH Mg(OH) 2(s) + 2NaCl C/TIE: Mg Cl + 2Na OH Mg(OH) 2(s) + 2Na Cl NI/PE: Mg OH Mg(OH) 2(s) Na 1+ + Cl 3. FE: Pb(NO 3 ) 2 + Li 2 SO 4 PbSO 4(s) + 2LiNO 3 C/TIE: Pb NO 3 + 2Li 1+ + SO 4 PbSO 4(s) + 2Li NO 3 NI/PE: Pb 2+ + SO 4 PbSO 4(s) Li FE: 2K 3 PO 4 + 3CuCl 2 Cu 3 (PO 4 ) 2 + 6KCl C/TIE: 6K PO 4 + 3Cu Cl Cu 3 (PO 4 ) 2 + 6K Cl NI/PE: 3Cu PO 4 Cu 3 (PO 4 ) 2 K 1+ + Cl 5. FE: NaC 2 H 3 O 2 + AgNO 3 AgC 2 H 3 O 2(s) + NaNO 3 C/TIE: Na 1+ + C 2 H 3 O 2 + Ag 1+ AgC 2 H 3 O 2(s) + Na 1+ NI/PE: Ag 1+ + C 2 H 3 O 2 AgC 2 H 3 O 2(s) Na FE: 2HBr + Cu 2 S 2CuBr (s) + H 2 S C/TIE: 2H Br + 2Cu 1+ + S 2CuBr (s) + 2H 1+ + S NI/PE: Cu 1+ + Br CuBr (s) H 1+ + S Required Practice 2 from page 3 1. FE: HCl + LiOH LiCl + H 2 O (l) C/TIE: H 1+ + Cl + Li 1+ + OH Li 1+ + Cl + H 2 O (l) NIE: H + + OH H 2 O (l) Li 1+ + Cl 2. FE: H 2 SO 4 + 2NaOH Na 2 SO 4 + 2H 2 O (l) C/TIE: 2H 1+ + SO 4 + 2Na OH 2Na 1+ + SO 4 + 2H 2 O (l) NIE: H + + OH H 2 O (l) Na 1+ + SO 4

5 CH 11 T49 MIXING SOLUTIONS 5 3. FE: HNO 3 + KOH KNO 3 + H 2 O (l) C/TIE: H 1+ + K 1+ + OH K 1+ + H 2 O (l) NIE: H + + OH H 2 O (l) K FE: 2HC 2 H 3 O 2 + Ba(OH) 2 Ba(C 2 H 3 O 2 ) 2 + 2H 2 O (l) C/TIE: 2H C 2 H 3 O 2 + Ba OH Ba C 2 H 3 O 2 + 2H 2 O (l) NIE: H + + OH H 2 O (l) Ba 2+ + C 2 H 3 O 2 5. FE: H 2 CO 3 + Sr(OH) 2 SrCO 3(s) + 2H 2 O (l) C/TIE: 2H 1+ + CO 3 + Sr OH SrCO 3(s) + 2H 2 O (l) NI/PE: 2H 1+ + CO 3 + Sr OH SrCO 3(s) + 2H 2 O (l) None 6. FE: 2H 3 PO 4 + 3Mg(OH) 2 Mg 3 (PO 4 ) 2(s) + 6H 2 O (l) C/TIE: 6H PO 3 + 3Mg OH Mg 3 (PO 4 ) 2(s) + 6H 2 O (l) NI/PE: 6H PO 3 + 3Mg OH Mg 3 (PO 4 ) 2(s) + 6H 2 O (l) None

6 CH 11 T49 MIXING SOLUTIONS 6 ASSIGNMENT At the top of your assignment, please print T49 Introducing Mixtures, your LAST then First name, block and date. Show all your work for questions requiring calculations; marks will not be awarded for final answers only. Complete these questions in the order given here. [Marks indicated in italicized brackets.] A. Write Balanced Formula equations, Complete Ionic Equations, Net Ionic Equations and state the Spectator Ions for the reactions between these reactants. [36] 1. Aqueous aluminum sulphate reacting with aqueous calcium hydroxide. 2. Aqueous sodium phosphate reacting with dissolved calcium bicarbonate. 3. Aqueous calcium hydroxide reacting with phosphoric acid. [36 marks in total] BE SURE YOU PREPARE FOR MEMORY CHALLENGE-7 ON T42 T51!!