Slide 1 / 20 Slide 2 / 20 New Jersey Center for Teaching and Learning AP Chemistry Progressive Science Initiative This material is made freely available at www.njctl.org and is intended for the non-commercial use of students and teachers. These materials may not be used for any commercial purpose without the written Unit 3: Presentation C permission of the owners. NJCTL maintains its website for the convenience of teachers who wish to Precipitation Reactions make their work available to other teachers, participate in a virtual professional learning community, and/or provide access to course materials to parents, students and others. Click to go to website: www.njctl.org www.njctl.org Slide 3 / 20 Slide 4 / 20 Types of Chemical Reactions Types of Reactions Chemical reactions are classified by what process is occurring by means of the reaction. What is occurring Type Example formation of solid Precipitation from mixing of two Co 2+ (aq) + 2OH - (aq) --> Co(OH) 2 (s) aqueous solution Acid/Base exchange of H + ions NH 4+ (aq) + OH - (aq) --> NH 3 (aq) + H 2 O(l) Seashells are created by the precipitation reaction below. exchange of Redox Mg(s) + Zn 2+ (aq) --> Mg 2+ (aq) + Zn(s) electrons Ca 2+ (aq) + CO 32- (aq) --> CaCO 3 (s) *Note: There are a few reactions that do not neatly fit into one of these categories. They will be dealt with later. Slide 5 / 20 Slide 6 / 20 Precipitation Reactions Precipitation Reactions When writing a precipitation reaction, a few simple steps must be In order to predict the products of a precipitation reaction, we must followed. know which ions tend to be soluble in water and which ones tend not Example: If aqueous solutions of potassium hydroxide and barium to be soluble. nitrate are mixed... Soluble unless Insoluble unless Soluble unless with Ag + , Hg + , paired with ion Always soluble with Ag + , Hg + , Picture what ions are present Pb 2+ , Ca 2+ , Sr 2+ , that always or Pb 2+ Ba 2+ dissolves K + (aq) + OH - (aq) + Ba 2+ (aq) + NO 3 -(aq) acetate hydroxide nitrate Decide which ions will form a ppt. and show the reaction of phosphate these ions only in the formation of the ppt. product nitrite chloride carbonate K + (aq) + OH - (aq) + Ba 2+ (aq) + NO 3 -(aq) ammonium bromide sulfate sulfide alkali metal ions iodide flouride 2OH - (aq) + Ba 2+ (aq) --> Ba(OH) 2 (s) chlorate sulfite bicarbonate Note: Ions not involved in the reaction are known as spectator ions. chromate The spectator ions here are K + (aq) and NO 3- (aq).
Slide 7 / 20 Slide 7 (Answer) / 20 1 What would be the product(s) of mixing aqueous 1 What would be the product(s) of mixing aqueous solutions of silver nitrate and sodium phosphate? solutions of silver nitrate and sodium phosphate? A AgNO 3 (s) A AgNO 3 (s) B Ag 3 PO 4 (s) and NaNO 3 (s) B Ag 3 PO 4 (s) and NaNO 3 (s) Answer D C NaNO 3 (s) C NaNO 3 (s) D Ag 3 PO 4 (aq) D Ag 3 PO 4 (aq) [This object is a pull tab] E Ag 3 PO 4 (aq) and NaNO 3 (aq) E Ag 3 PO 4 (aq) and NaNO 3 (aq) Slide 8 / 20 Slide 8 (Answer) / 20 2 If aqueous mixtures of ammonium fluoride and calcium 2 If aqueous mixtures of ammonium fluoride and calcium nitrate are mixed, which two ions would be spectator nitrate are mixed, which two ions would be spectator ions? ions? A Ca 2+ and NO 3 - A Ca 2+ and NO 3 - Answer C B Ca 2+ and NH 4 + B Ca 2+ and NH 4 + C NH 4 + and NO 3 - C NH 4 + and NO 3 - D NH 4 + and Ca 2+ D NH 4 + and Ca 2+ [This object is a pull tab] E Ca 2+ and F - E Ca 2+ and F - Slide 9 / 20 Slide 9 (Answer) / 20 3 Which of the following aqueous solutions would form a 3 Which of the following aqueous solutions would form a precipitate if mixed with an solution of strontium chloride? precipitate if mixed with an solution of strontium chloride? I. AgNO 3 (aq) I. AgNO 3 (aq) A I only A I only II. Ca(NO 3 ) 2 (aq) II. Ca(NO 3 ) 2 (aq) B II only B II only Answer D III. NaOH(aq) III. NaOH(aq) C III only C III only D I and III only D I and III only E II and III only E II and III only [This object is a pull tab]
Slide 10 / 20 Slide 10 (Answer) / 20 4 Which of the following would be the correct reaction 4 Which of the following would be the correct reaction when aqueous solutions of lead(II)acetate and when aqueous solutions of lead(II)acetate and magnesium sulfate are mixed? magnesium sulfate are mixed? Answer A A Pb 2+ (aq) + SO 42- (aq) --> PbSO 4 (s) A Pb 2+ (aq) + SO 42- (aq) --> PbSO 4 (s) B Mg 2+ (aq) + Pb 2+ (aq) --> PbMg(s) B Mg 2+ (aq) + Pb 2+ (aq) --> PbMg(s) [This object is a pull tab] C Mg 2+ (aq) + C 2 H 3 O 2 -(aq) --> Mg(C 2 H 3 O 2 ) 2 (s) C Mg 2+ (aq) + C 2 H 3 O 2 -(aq) --> Mg(C 2 H 3 O 2 ) 2 (s) D Pb 2+ (aq) + SO 42- (aq) + Mg 2+ (aq) + C 2 H 3 O 2 -(aq) --> PbSO 4 (s) D Pb 2+ (aq) + SO 42- (aq) + Mg 2+ (aq) + C 2 H 3 O 2 -(aq) --> PbSO 4 (s) Slide 11 / 20 Slide 11 (Answer) / 20 5 If aqueous solutions of magnesium iodide are sodium 5 If aqueous solutions of magnesium iodide are sodium phosphate are mixed and the resulting solution filtered, phosphate are mixed and the resulting solution filtered, what ions would be present dissolved in the filtrate? what ions would be present dissolved in the filtrate? A magnesium ion and phosphate ions A magnesium ion and phosphate ions Answer B magnesium ion and iodide ion B magnesium ion and iodide ion C C sodium ion and iodide ion C sodium ion and iodide ion D sodium ion and magnesium ion D sodium ion and magnesium ion [This object is a pull tab] E sodium ion and phosphate ion E sodium ion and phosphate ion Slide 12 / 20 Slide 13 / 20 Precipitation Reactions 6 Two aqueous solutions are mixed forming a black precipitate. Which of the following could be the correct A number of precipitates have signature colors and can be identity of the two aqueous solutions? identified by them. Precipitate Color A Pb(NO 3 ) 2 (aq) and AgNO 3 (aq) PbI 2 (s) Yellow AgI(s) Yellow B NaI(aq) and AgNO 3 (aq) Cu(OH) 2 (s) Blue C CuNO 3 (aq) and MgSO 4 (aq) Ag 2 S(s) Black CuO(s) Black D AgC 2 H 3 O 2 (aq) and K 2 S(aq) PbCrO 4 (s) Yellow E Sr(NO 3 ) 2 (aq) and KOH(aq) AgBr(s) Cream
Slide 13 (Answer) / 20 Slide 14 / 20 6 Two aqueous solutions are mixed forming a black 7 An aqueous solution "A" will form a yellow precipitate precipitate. Which of the following could be the correct when mixed with aqueous solution "B" and no precipitate identity of the two aqueous solutions? at all when mixed with solution "C". What could be the identity of the three solutions? A Pb(NO 3 ) 2 (aq) and AgNO 3 (aq) Answer A MgSO 4 (aq) Pb(NO 3 ) 2 (aq) NH 4 F(aq) D B NaI(aq) and AgNO 3 (aq) B NH 4 I(aq) AgNO 3 (aq) KF(aq) C CuNO 3 (aq) and MgSO 4 (aq) C AgNO 3 (aq) NH 4 I(aq) KF(aq) D AgC 2 H 3 O 2 (aq) and K 2 S(aq) [This object is a pull tab] D NaI(aq) Pb(NO 3 ) 2 (aq) NH 4 F(aq) E Sr(NO 3 ) 2 (aq) and KOH(aq) Slide 14 (Answer) / 20 Slide 15 / 20 Precipitation Reactions 7 An aqueous solution "A" will form a yellow precipitate when mixed with aqueous solution "B" and no precipitate The amount of precipitate made and concentration of ions left in at all when mixed with solution "C". What could be the solution can be determined using basic stoichiometry. identity of the three solutions? Answer B For example: What is the concentration of all ions left in A MgSO 4 (aq) Pb(NO 3 ) 2 (aq) NH 4 F(aq) solution after 200 mL of 0.1 M CaBr 2 (aq) is mixed with 200 mL of 0.2 M Pb(NO 3 ) 2 (aq)? B NH 4 I(aq) AgNO 3 (aq) KF(aq) Pb 2+ (aq) + 2Br - (aq) --> PbBr 2 (s) [This object is a pull tab] C AgNO 3 (aq) NH 4 I(aq) KF(aq) Find mole amounts after writing reaction. D NaI(aq) Pb(NO 3 ) 2 (aq) NH 4 F(aq) 0.2 L x 0.1 n/L x 1 = 0.02 mol Ca 2+ (aq) 0.2 L x 0.1 n/L x 2 = 0.04 mol Br - (aq) 0.2 L x 0.2 n/L x 1 = 0.04 mol Pb 2+ (aq) 0.2 L x 0.2 n/L x 2 = 0.08 mol NO 3 -(aq) Slide 16 / 20 Slide 17 / 20 Precipitation Reactions 8 What mass of CaSO 4 precipitate can be formed when 50 mL of 0.2 M Ca(NO 3 ) 2 mix with 50 mL of 0.3 M Na 2 SO 4 ? Find concentrations of spectator ions by dividing by total volume after mixing A 0.136 g 0.02 mol Ca 2+ (aq)/0.4 L = 0.050 M 0.08 mol NO 3 -(aq)/0.4 L = 0.200 M B 1.36 g Determine limiting and excess reactants and find concentration of C 2.72 g excess ion by dividing by total volume D 2.04 g 0.04 mol Pb 2+ x 2 mol Br - needed = 0.08 mol Br - needed Only 0.04 mol Br- available so.... Br - - Limits Pb 2+ - Excess E 0.204 g 0.04 mol Br - x 1/2 mol Pb 2+ needed = 0.02 mol Pb 2+ needed 0.04 mol Pb 2+ - 0.02 mol Pb 2+ = 0.02 mol Pb 2+ /0.4 L = 0.050 M
Recommend
More recommend
