Slide 1 / 20 New Jersey Center for Teaching and Learning 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 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: www.njctl.org Slide 2 / 20 AP Chemistry Unit 3: Presentation C Precipitation Reactions www.njctl.org Slide 3 / 20 Types of Chemical Reactions Seashells are created by the precipitation reaction below. Ca 2+ (aq) + CO 32- (aq) --> CaCO 3 (s)
Slide 4 / 20 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) exchange of Redox Mg(s) + Zn 2+ (aq) --> Mg 2+ (aq) + Zn(s) electrons *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 Precipitation Reactions 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. Soluble unless Insoluble unless Soluble unless with Ag + , Hg + , paired with ion Always soluble with Ag + , Hg + , Pb 2+ , Ca 2+ , Sr 2+ , that always or Pb 2+ Ba 2+ dissolves acetate hydroxide nitrate phosphate nitrite chloride carbonate ammonium bromide sulfate sulfide alkali metal ions iodide flouride chlorate sulfite bicarbonate chromate Slide 6 / 20 Precipitation Reactions 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) + NO 3 -(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) + NO 3 -(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 NO 3- (aq).
Slide 7 / 20 1 What would be the product(s) of mixing aqueous solutions of silver nitrate and sodium phosphate? A AgNO 3 (s) B Ag 3 PO 4 (s) and NaNO 3 (s) C NaNO 3 (s) D Ag 3 PO 4 (aq) E Ag 3 PO 4 (aq) and NaNO 3 (aq) Slide 7 (Answer) / 20 1 What would be the product(s) of mixing aqueous solutions of silver nitrate and sodium phosphate? A AgNO 3 (s) B Ag 3 PO 4 (s) and NaNO 3 (s) Answer D C NaNO 3 (s) D Ag 3 PO 4 (aq) [This object is a pull tab] E Ag 3 PO 4 (aq) and NaNO 3 (aq) Slide 8 / 20 2 If aqueous mixtures of ammonium fluoride and calcium nitrate are mixed, which two ions would be spectator ions? 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 -
Slide 8 (Answer) / 20 2 If aqueous mixtures of ammonium fluoride and calcium nitrate are mixed, which two ions would be spectator ions? A Ca 2+ and NO 3 - Answer C B Ca 2+ and NH 4 + C NH 4 + and NO 3 - D NH 4 + and Ca 2+ [This object is a pull tab] E Ca 2+ and F - Slide 9 / 20 3 Which of the following aqueous solutions would form a precipitate if mixed with an solution of strontium chloride? I. AgNO 3 (aq) A I only II. Ca(NO 3 ) 2 (aq) B II only III. NaOH(aq) C III only D I and III only E II and III only Slide 9 (Answer) / 20 3 Which of the following aqueous solutions would form a precipitate if mixed with an solution of strontium chloride? I. AgNO 3 (aq) A I only II. Ca(NO 3 ) 2 (aq) B II only Answer D III. NaOH(aq) C III only D I and III only E II and III only [This object is a pull tab]
Slide 10 / 20 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 42- (aq) --> PbSO 4 (s) B Mg 2+ (aq) + Pb 2+ (aq) --> PbMg(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) Slide 10 (Answer) / 20 4 Which of the following would be the correct reaction when aqueous solutions of lead(II)acetate and magnesium sulfate are mixed? Answer A A Pb 2+ (aq) + SO 42- (aq) --> PbSO 4 (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) D Pb 2+ (aq) + SO 42- (aq) + Mg 2+ (aq) + C 2 H 3 O 2 -(aq) --> PbSO 4 (s) Slide 11 / 20 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? 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
Slide 11 (Answer) / 20 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? A magnesium ion and phosphate ions Answer B magnesium ion and iodide ion C C sodium ion and iodide ion D sodium ion and magnesium ion [This object is a pull tab] E sodium ion and phosphate ion Slide 12 / 20 Precipitation Reactions A number of precipitates have signature colors and can be identified by them. Precipitate Color PbI 2 (s) Yellow AgI(s) Yellow Cu(OH) 2 (s) Blue Ag 2 S(s) Black CuO(s) Black PbCrO 4 (s) Yellow AgBr(s) Cream Slide 13 / 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? 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 2 H 3 O 2 (aq) and K 2 S(aq) E Sr(NO 3 ) 2 (aq) and KOH(aq)
Slide 13 (Answer) / 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? A Pb(NO 3 ) 2 (aq) and AgNO 3 (aq) Answer D B NaI(aq) and AgNO 3 (aq) C CuNO 3 (aq) and MgSO 4 (aq) D AgC 2 H 3 O 2 (aq) and K 2 S(aq) [This object is a pull tab] E Sr(NO 3 ) 2 (aq) and KOH(aq) Slide 14 / 20 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? A MgSO 4 (aq) Pb(NO 3 ) 2 (aq) NH 4 F(aq) B NH 4 I(aq) AgNO 3 (aq) KF(aq) C AgNO 3 (aq) NH 4 I(aq) KF(aq) D NaI(aq) Pb(NO 3 ) 2 (aq) NH 4 F(aq) Slide 14 (Answer) / 20 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? Answer B A MgSO 4 (aq) Pb(NO 3 ) 2 (aq) NH 4 F(aq) B NH 4 I(aq) AgNO 3 (aq) KF(aq) [This object is a pull tab] C AgNO 3 (aq) NH 4 I(aq) KF(aq) D NaI(aq) Pb(NO 3 ) 2 (aq) NH 4 F(aq)
Slide 15 / 20 Precipitation Reactions 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 NO 3 -(aq) Slide 16 / 20 Precipitation Reactions Find concentrations of spectator ions by dividing by total volume after mixing 0.02 mol Ca 2+ (aq)/0.4 L = 0.050 M 0.08 mol NO 3 -(aq)/0.4 L = 0.200 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 2+ - 0.02 mol Pb 2+ = 0.02 mol Pb 2+ /0.4 L = 0.050 M Slide 17 / 20 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 ? A 0.136 g B 1.36 g C 2.72 g D 2.04 g E 0.204 g
Slide 17 (Answer) / 20 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 ? A 0.136 g Answer B B 1.36 g C 2.72 g D 2.04 g [This object is a pull tab] E 0.204 g Slide 18 / 20 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 4 F is mixed with 700 mL of 0.1 M SrI 2 (aq)? 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- Slide 18 (Answer) / 20 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 4 F is mixed with 700 mL of 0.1 M SrI 2 (aq)? A F- < Sr 2+ < I- < NH 4+ Answer E B Sr 2+ < F- < NH 4+ < I- C F- < Sr 2+ < NH 4+ < I- D NH 4+ < F- < Sr 2+ < I- [This object is a pull tab] E F- < NH 4+ < Sr 2+ < I-
Recommend
More recommend
