Unit 3: Presentation C Precipitation Reactions

Transcription

1 New Jersey Center for Teaching and Learning Slide 1 / 20 Progressive Science Initiative This material is made freely available at 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 permission of the owners. NJCTL maintains its website for the convenience of teachers who wish to 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: Slide 2 / 20 AP Chemistry Unit 3: Presentation C Precipitation Reactions Types of Chemical Reactions Slide 3 / 20 Seashells are created by the precipitation reaction below. Ca 2+ (aq) + CO 3 2- (aq) --> CaCO 3 (s)

2 Types of Reactions Chemical reactions are classified by what process is occurring by means of the reaction. Slide 4 / 20 Type What is occurring Example Precipitation formation of solid from mixing of two aqueous solution Co 2+ (aq) + 2OH - (aq) --> Co(OH)2(s) Acid/Base exchange of H + ions NH4 + (aq) + OH - (aq) --> NH3(aq) + H2O(l) Redox exchange of electrons Mg(s) + Zn 2+ (aq) --> Mg 2+ (aq) + Zn(s) *Note: There are a few reactions that do not neatly fit into one of these categories. They will be dealt with later. Precipitation Reactions Slide 5 / 20 In order to predict the products of a precipitation reaction, we must know which ions tend to be soluble in water and which ones tend not to be soluble. Always soluble acetate nitrate nitrite ammonium alkali metal ions chlorate bicarbonate Soluble unless with Ag +, Hg +, or Pb 2+ chloride bromide iodide Soluble unless with Ag +, Hg +, Pb 2+, Ca 2+, Sr 2+, Ba 2+ sulfate Insoluble unless paired with ion that always dissolves hydroxide phosphate carbonate sulfide flouride sulfite chromate Precipitation Reactions Slide 6 / 20 When writing a precipitation reaction, a few simple steps must be followed. Example: If aqueous solutions of potassium hydroxide and barium nitrate are mixed... Picture what ions are present K + (aq) + OH - (aq) + Ba 2+ (aq) + NO3-(aq) Decide which ions will form a ppt. and show the reaction of these ions only in the formation of the ppt. product K + (aq) + OH - (aq) + Ba 2+ (aq) + NO3-(aq) 2OH - (aq) + Ba 2+ (aq) --> Ba(OH)2(s) Note: Ions not involved in the reaction are known as spectator ions. The spectator ions here are K + (aq) and NO3 - (aq).

3 1 What would be the product(s) of mixing aqueous solutions of silver nitrate and sodium phosphate? Slide 7 / 20 A AgNO 3(s) B Ag 3PO 4(s) and NaNO 3(s) C NaNO 3(s) D Ag 3PO 4(aq) E Ag 3PO 4(aq) and NaNO 3(aq) 1 What would be the product(s) of mixing aqueous solutions of silver nitrate and sodium phosphate? Slide 7 () / 20 A AgNO 3(s) B Ag 3PO 4(s) and NaNO 3(s) C NaNO 3(s) D D Ag 3PO 4(aq) E Ag 3PO 4(aq) and NaNO 3(aq) 2 If aqueous mixtures of ammonium fluoride and calcium nitrate are mixed, which two ions would be spectator ions? Slide 8 / 20 A Ca 2+ and NO 3- B Ca 2+ and NH 4+ C NH 4+ and NO 3- D NH 4+ and Ca 2+ E Ca 2+ and F -

4 2 If aqueous mixtures of ammonium fluoride and calcium nitrate are mixed, which two ions would be spectator ions? Slide 8 () / 20 A Ca 2+ and NO 3- B Ca 2+ and NH 4+ C NH 4+ and NO 3- D NH 4+ and Ca 2+ C E Ca 2+ and F - 3 Which of the following aqueous solutions would form a precipitate if mixed with an solution of strontium chloride? Slide 9 / 20 A I only B II only C III only I. AgNO 3 (aq) II. Ca(NO 3 ) 2 (aq) III. NaOH(aq) D I and III only E II and III only 3 Which of the following aqueous solutions would form a precipitate if mixed with an solution of strontium chloride? Slide 9 () / 20 A I only B II only C III only D I and III only E II and III only I. AgNO 3 (aq) II. Ca(NO 3 ) 2 (aq) D III. NaOH(aq)

5 4 Which of the following would be the correct reaction when aqueous solutions of lead(ii)acetate and magnesium sulfate are mixed? Slide 10 / 20 A Pb 2+ (aq) + SO 2-4 (aq) --> PbSO 4(s) B Mg 2+ (aq) + Pb 2+ (aq) --> PbMg(s) C Mg 2+ (aq) + C 2H 3O 2-(aq) --> Mg(C 2H 3O 2) 2(s) D Pb (aq) + SO 4 (aq) + Mg 2+ (aq) + C 2H 3O 2-(aq) --> PbSO 4(s) 4 Which of the following would be the correct reaction when aqueous solutions of lead(ii)acetate and magnesium sulfate are mixed? A Pb 2+ (aq) + SO 4 2- (aq) --> PbSO 4(s) A Slide 10 () / 20 B Mg 2+ (aq) + Pb 2+ (aq) --> PbMg(s) C Mg 2+ (aq) + C 2H 3O 2-(aq) --> Mg(C 2H 3O 2) 2(s) D Pb 2+ (aq) + SO 4 2- (aq) + Mg 2+ (aq) + C 2H 3O 2-(aq) --> PbSO 4(s) 5 If aqueous solutions of magnesium iodide are sodium phosphate are mixed and the resulting solution filtered, what ions would be present dissolved in the filtrate? Slide 11 / 20 A magnesium ion and phosphate ions B magnesium ion and iodide ion C sodium ion and iodide ion D sodium ion and magnesium ion E sodium ion and phosphate ion

6 5 If aqueous solutions of magnesium iodide are sodium phosphate are mixed and the resulting solution filtered, what ions would be present dissolved in the filtrate? Slide 11 () / 20 A magnesium ion and phosphate ions B magnesium ion and iodide ion C sodium ion and iodide ion C D sodium ion and magnesium ion E sodium ion and phosphate ion Precipitation Reactions A number of precipitates have signature colors and can be identified by them. Precipitate PbI 2(s) AgI(s) Cu(OH) 2(s) Ag 2S(s) CuO(s) PbCrO 4(s) AgBr(s) Color Yellow Yellow Blue Black Black Yellow Cream Slide 12 / 20 6 Two aqueous solutions are mixed forming a black precipitate. Which of the following could be the correct identity of the two aqueous solutions? Slide 13 / 20 A Pb(NO 3) 2(aq) and AgNO 3(aq) B NaI(aq) and AgNO 3(aq) C CuNO 3(aq) and MgSO 4(aq) D AgC 2H 3O 2(aq) and K 2S(aq) E Sr(NO 3) 2(aq) and KOH(aq)

7 6 Two aqueous solutions are mixed forming a black precipitate. Which of the following could be the correct identity of the two aqueous solutions? Slide 13 () / 20 A Pb(NO 3) 2(aq) and AgNO 3(aq) B NaI(aq) and AgNO 3(aq) D C CuNO 3(aq) and MgSO 4(aq) D AgC 2H 3O 2(aq) and K 2S(aq) E Sr(NO 3) 2(aq) and KOH(aq) 7 An aqueous solution "A" will form a yellow precipitate when mixed with aqueous solution "B" and no precipitate at all when mixed with solution "C". What could be the identity of the three solutions? Slide 14 / 20 A MgSO 4(aq) Pb(NO 3) 2(aq) NH 4F(aq) B NH 4I(aq) AgNO 3(aq) KF(aq) C AgNO 3(aq) NH 4I(aq) KF(aq) D NaI(aq) Pb(NO 3) 2(aq) NH 4F(aq) 7 An aqueous solution "A" will form a yellow precipitate when mixed with aqueous solution "B" and no precipitate at all when mixed with solution "C". What could be the identity of the three solutions? B A MgSO 4(aq) Pb(NO 3) 2(aq) NH 4F(aq) Slide 14 () / 20 B NH 4I(aq) AgNO 3(aq) KF(aq) C AgNO 3(aq) NH 4I(aq) KF(aq) D NaI(aq) Pb(NO 3) 2(aq) NH 4F(aq)

8 Precipitation Reactions Slide 15 / 20 The amount of precipitate made and concentration of ions left in solution can be determined using basic stoichiometry. For example: What is the concentration of all ions left in 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)? Pb 2+ (aq) + 2Br - (aq) --> PbBr 2(s) Find mole amounts after writing reaction. 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 NO3-(aq) Precipitation Reactions Slide 16 / 20 Find concentrations of spectator ions by dividing by total volume after mixing 0.02 mol Ca 2+ (aq)/0.4 L = M 0.08 mol NO 3-(aq)/0.4 L = M Determine limiting and excess reactants and find concentration of excess ion by dividing by total volume 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 0.04 mol Br - x 1/2 mol Pb 2+ needed = 0.02 mol Pb 2+ needed 0.04 mol Pb mol Pb 2+ = 0.02 mol Pb 2+ /0.4 L =0.050 M 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 2SO 4? Slide 17 / 20 A g B 1.36 g C 2.72 g D 2.04 g E g

9 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 2SO 4? Slide 17 () / 20 A g B 1.36 g C 2.72 g D 2.04 g E g B 9 What would be the correct order of ions from highest to lowest concentration in the solution after 300 ml of 0.1 M NH 4F is mixed with 700 ml of 0.1 M SrI 2(aq)? Slide 18 / 20 A F- < Sr 2+ + < I- < NH 4 B Sr 2+ < F- < NH + 4 < I- C F- < Sr 2+ < NH + 4 < I- D NH + 4 < F- < Sr 2+ < I- + E F- < NH 4 < Sr 2+ < I- 9 What would be the correct order of ions from highest to lowest concentration in the solution after 300 ml of 0.1 M NH 4F is mixed with 700 ml of 0.1 M SrI 2(aq)? Slide 18 () / 20 A F- < Sr 2+ < I- < NH 4 + B Sr 2+ < F- < NH 4 + < I- C F- < Sr 2+ < NH + 4 < I- D NH + 4 < F- < Sr 2+ < I- E E F- < NH 4 + < Sr 2+ < I-

10 10 How many ml of 0.4 M AgNO 3 solution must be added to 200 ml of 0.4 M NaI in order to form 11.7 grams of AgI precipitate? Slide 19 / 20 A 200 ml B 20 ml C 250 ml D 125 ml E 12.5 ml 10 How many ml of 0.4 M AgNO 3 solution must be added to 200 ml of 0.4 M NaI in order to form 11.7 grams of AgI precipitate? Slide 19 () / 20 A 200 ml B 20 ml C 250 ml D 125 ml E 12.5 ml D Slide 20 / 20