Advanced Placement Chemistry, SCH4UAP EXAMINATION REVIEW. Equations. Page 1

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1 Advanced Placement Chemistry, SCH4UAP EXAMINATION REVIEW Equations Page 1

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7 4.2 - Precipitation Reactions Question 1 Give the formulas to show the reactants and the products for each of the following chemical reactions. Each of the reactions occurs in aqueous solution unless otherwise indicated. Represent substances in solution as ions if the substance is extensively ionized. Omit formulas for any ions or molecules that are unchanged by the reaction. In all cases a reaction occurs. You need not balance. a) A solution of copper(ii) sulfate is added to a solution of barium hydroxide. [1991 exam] b) Solutions of strontium nitrate and sodium sulphate are mixed. [2001 exam] c) A solution of copper(ii) chloride is added to a solution of sodium sulphide [2000 exam] d) Solutions of sodium iodide and lead nitrate are mixed [1990 exam] e) Solutions of tri-potassium phosphate and zinc nitrate are mixed. [1993 exam] f) Solutions of silver nitrate and lithium bromide are mixed. [1989 exam] Answers to Question 1 a) Cu 2+ + OH - Cu(OH) 2 b) Sr 2+ + SO 4 2- SrSO 4 c) Cu 2+ + S 2- CuS d) Pb 2+ + I - PbI 2 e) Zn 2+ + PO 4 3- Zn 3 (PO 4 ) 2 f) Ag + + Br - AgBr Question 2 [AP, 1984] The net ionic equation for the reaction between silver carbonate and hydrochloric acid is: (A) Ag 2 CO 3 (s) + 2 H Cl ---> 2 AgCl(s) + H 2 O + CO(g) (B) 2 Ag + + CO H Cl ---> 2 AgCl(s) + H 2 O + CO 2 (g) (C) CO H + ---> H 2 O + CO 2 (g) (D) Ag + + Cl ---> AgCl(s) (E) Ag 2 CO 3 (s) + 2 H + ---> 2Ag + + H 2 CO 3 Page 7

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11 Strong and Weak Acids and Bases Strong and Weak Acids A small percentage of all acids are considered to be strong acids, acids that are completely ionized in aqueous solution. All of the remaining common acids are weak acids, meaning that, when they are dissolved in water, only a small percentage of the molecules dissociate into ions. Strong acids are strong electrolytes; weak acids are weak electrolytes. LEARN the Big Six Strong Acids HClO 4 (perchloric acid) HNO 3 (nitric acid) HCl, HBr, HI (hydrochloric, hydrobromic, and hydroiodic acids) H 2 SO 4 (sulphuric acid) As far as the AP Chemistry course is concerned, these six are the only strong acids that you are required to know. Since they completely ionize, they should always be written in ionic form in an equation (either as reactants or as products). It is safe to assume that any other acid that you come across in this course will be a weak (or moderate ) acid and it should, therefore, be written in molecular, rather than ionic, form. Two common examples of moderate acids that you should know are: H 3 PO 4 (phosphoric acid) (COOH) 2 (oxalic acid) Page 11

12 By definition, the strong acids are 100% ionized in aqueous solution and should, therefore, always be written in ionic, rather than molecular, form. In other words, strong acids should be written as represented on the right hand side of the following equations: (perchloric acid) HClO 4 (aq) + H 2 O(l) ---> H 3 O + (aq) + ClO - 4 (aq) (nitric acid) HNO 3 (aq) + H 2 O(l) ---> H 3 O + (aq) + NO - 3 (aq) (hydrochloric acid) HCl(aq) + H 2 O(l) ---> H 3 O + (aq) + Cl - (aq) (hydrobromic acid) HBr(aq) + H 2 O(l) ---> H 3 O + (aq) + Br - (aq) (hydroiodic acid) HI(aq) + H 2 O(l) ---> H 3 O + (aq) + I - (aq) (sulphuric acid) H 2 SO 4 (aq) + 2 H 2 O(l) ---> 2 H 3 O + (aq) + SO 2-4 (aq) By definition, the weak acids are only slightly ionized in aqueous solution and should, therefore, always be written in molecular, rather than ionic, form. In other words, they should be written as represented on the left hand side of the following equations (note the double arrows!): (hydrofluoric acid) HF(aq) + H 2 O(l) <--> H 3 O + (aq) + F - (aq) (carbonic acid) H 2 CO 3 (aq) + 2 H 2 O(l) <--> 2 H 3 O + (aq) + CO 2-3 (aq) (phosphoric acid) H 3 PO 4 (aq) + 3 H 2 O(l) <--> 3 H 3 O + (aq) + PO 3-4 (aq) The majority of weak acids are organic (carboxylic) acids. YOU WILL LEARN A LOT MORE ABOUT WEAK ACIDS LATER IN THIS UNIT! It is worth remembering at this time that acidic solutions are also created by certain substances that react with water to form H + (aq)ions. You have already learned that non-metal oxides react with water to form acidic solutions. For example: SO 2 (g) + H 2 O(l) SO 3 2- (aq) + 2H + (aq) Page 12

13 Strong and Weak Bases Strong bases are bases that produce a high concentration of OH - (aq) ions in aqueous solution. As with strong acids, there are also relatively few common strong bases. Soluble hydroxides and soluble carbonates will produce strong bases. Since most hydroxides have low solubilities, very few hydroxides form strong bases. The hydroxides of the Group IA Alkali Metals have high solubilities and, therefore, produce strong bases; Ba(OH) 2 and Sr(OH) 2 are moderately soluble hydroxides that produce moderately strong bases. Learn these five important Strong Bases: LiOH, NaOH, KOH, Ba(OH) 2, Sr(OH) 2 Soluble carbonates (which, for all practical purposes, means the carbonates of the Group IA Alkali metals also produce moderately strong bases when dissolved in water since the carbonate ion reacts with water molecules according to the equation: CO 3 2- (aq) + H 2 O (l) ----> HCO 3 - (aq) + OH - (aq) Strongly basic solutions are also created by certain substances that react with water to form OH (aq)ions. The most common of these contain the oxide ion. You have already learned that metal oxides react with water to form basic solutions. For example: K 2 O(s) + H 2 O(l) 2 K + (aq) + 2 OH - (aq) Ionic hydrides also react with H 2 O to form OH. For example: LiH + H 2 O ---> Li + + OH - + H 2 Page 13

14 AP Question Give the formulas to show the reactants and the products for each of the following chemical reactions. Each of the reactions occurs in aqueous solution unless otherwise indicated. Represent substances in solution as ions if the substance is extensively ionized. Omit formulas for any ions or molecules that are unchanged by the reaction. In all cases a reaction occurs. You need not balance. Answers 1. Solid cesium oxide is added to water. [2002, Form A] 2. Sulphur dioxide gas is bubbled into a beaker of water. [2002, Form B] 3. Solid calcium hydride is added to distilled water. [1995] 4. Phosphorous(V) oxide powder is sprinkled over distilled water. [1994] 5. Sulfur trioxide gas is added to excess water. [1988] 6. Powdered strontium oxide is added to distilled water. [2000] 7. Calcium oxide powder is added to distilled water. [1999] 8. Solid sodium oxide is added to distilled water. [1998] 9. Drops of liquid dinitrogen trioxide are added to distilled water. [1996] 10. Solid lithium hydride is added to water. [1992] 11. Samples of boron trichloride gas and ammonia gas are mixed. [1989] 1. Cs 2 O + H 2 O Cs + + OH - (Note: Alkali metal hydroxides are soluble) 2. SO 2 + H 2 O H 2 SO 3 (Note: H 2 SO 3 is a weak acid and is written in molecular, not ionic, form) 3. CaH 2 + H 2 O --> Ca(OH) 2 + H 2 (Note: Ca(OH) 2 is only slightly soluble!) 4. P 4 O 10 + H 2 O ---> H 3 PO 4 (Note: H 3 PO 4 is a moderateacid and is written in molecular, not ionic, form) 5. SrO + H 2 O Sr 2+ + OH - (or Sr(OH) 2 since it is not very soluble!) 6. CaO + H 2 O Ca(OH) 2 (Note: Ca(OH) 2 is only slightly soluble!) 7. Na 2 O + H 2 O Na + + OH - (Note: Alkali metal hydroxides are soluble) 8. N 2 O 3 + H 2 O ---> HNO 2 (Note: HNO 2 is a weak acid and is written in molecular, not ionic, form) 9. LiH + H 2 O ---> Li + + OH - + H BCl 3 + NH 3 ---> Cl 3 BNH SO 3 + H 2 O H + + SO 4 2- (Note: H 2 SO 4 is a strong acid and is written in ionic, not molecular, form) Page 14

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25 Equations for Reactions Involving Metals Reaction of Metals with Nonmetals Such reactions are examples of Combination Reactions. They are also Redox Reactions (later in the course!). For example: Zn + I 2 Note: When reactions occur between metals such as Fe, Cu, & Sn that can form multiple ions (Fe 2+ & Fe 3+ ; Cu + & Cu 2+ ; Sn 2+ & Sn 4+, etc.) and reactive nonmetals, such as O 2, Cl 2 & F 2, the metal will always be oxidised to the ion with the higher positive charge. For example: Fe + Cl 2 Reaction of Metals with Water (or Steam) The metal atoms are oxidized to metal ions. The water molecules are reduced (2H 2 O + 2e - ---> 2OH - + H 2 ) For example... Na + H 2 O ---> + OH - + H 2 Ca + H 2 O ---> + OH - + H 2 Reaction of Metals with Dilute Acids The metal atoms are oxidized to metal ions. The hydrogen ions in the acid are reduced (2H + + 2e - ---> H 2 ) The anions in the acid are spectator ions. For example... Na + H + ---> Na + + H 2 Ca + H + ---> Ca 2+ + H 2 Page 25

26 Reaction of Metals with Metal Salt Solutions (Single Displacement Reactions) The metal atoms are oxidized to metal ions. The metal ions are reduced to metal atoms. The anions combined originally with the metallic cations are spectator ions. For example... Cu + Ag + ---> Cu 2+ + Ag Al + Cu > Al 3+ + Cu (Special) Reactions involving Fe 2+ and Fe 3+ ions Fe(s) + 2 Fe 3+ (aq) ----> 3 Fe 2+ (aq) Fe 2+ (aq) + Cl 2 (aq) ----> Fe 3+ (aq) + 2 Cl - (aq) Page 26

27 Questions Give the formulas to show the reactants and the products for the following chemical equations. Each of the reactions occurs in aqueous solution unless otherwise indicated. Represent substances in solution as ions if the substance is extensively ionized. Omit formulas for any ions or molecules that are unchanged by the reaction. In all cases a reaction occurs. You need not balance. a) Pure solid phosphorus (white form) is burned in air. b) Calcium metal is strongly heated in nitrogen gas. c) A piece of aluminum metal is added to a solution of silver nitrate. d) A small piece of calcium metal is added to hot distilled water (2000). e) Zinc metal is added to a solution of copper(ii) nitrate. f) A mixture of powdered iron (III) oxide and powdered aluminum is heated strongly (1999) ANSWERS a. P 4 + O 2 P 4 O 10 b. Ca + N 2 ---> Ca 3 N 2 c. Al + Ag > Al 3+ + Ag d. Ca + H 2 O Ca 2+ + H 2 + OH - e. Zn + Cu 2+ Zn 2+ + Cu f. Fe 2 O 3 + A o Fe + Al 2 O 3 Page 27

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33 Name: AP Chemistry Chemical Equations Worksheet Write the balanced chemical equation (excluding spectator ions) underneath each reaction description, and answer the question. (a) A solution of ammonia is added to a dilute solution of acetic acid. Identify the conjugate acid base pairs in this reaction. (b) Solutions of sodium hydroxide and acetic acid are mixed. Acetic acid is a weak acid. If equal volumes of equal molar solutions are mixed, will the solution ph be >7, 7, or <7? Explain. (c) Hydrogen sulfide gas is bubbled through excess potassium hydroxide solution. Write the successive ionization equations for H 2 S. (d) Solid barium oxide is added to distilled water. Is the resulting solution acidic, basic or neutral? Explain. (e) Solid calcium oxide is exposed to a stream of carbon dioxide gas. What type of reaction has occurred? (f) Solid dinitrogen pentoxide is added to water. Is the final solution acidic, basic or neutral? Explain. (g) Carbon disulfide vapor is burned in excess oxygen. What is the oxidizing agent in this reaction? 1 Your Safer Source for Science Supplies Publication No Flinn Scientific, Inc. All Rights Reserved. (800) Fax: (866) P.O. Box 219 Batavia, IL flinn@flinnsci.com

34 (h) Lithium metal is burned in air. Besides combustion, what type of reaction could this be classified as? (i) A solution of diamminesilver(i) chloride is treated with dilute nitric acid. What is the driving force for this reaction? (j) A concentrated solution of ammonia is added to a suspension of zinc hydroxide. What are the possible molecular geometries for the complex ion product? (k) Excess concentrated sodium hydroxide solution is added to solid aluminum hydroxide. Name any complex ion formed in the reaction. (l) Solid ammonium carbonate is heated. Classify the type of reaction occurring. (m) A solution of hydrogen peroxide is catalytically decomposed. Name the element being reduced and the element being oxidized. (n) A solution of potassium iodide is electrolyzed. At which electrode would a gas be released? (o) A solution of copper(ii) sulfate is electrolyzed using inert electrodes. Is the final solution acidic, basic or neutral? (p) A solution of ammonium sulfate is added to a saturated solution of barium hydroxide. Identify any precipitate formed in the reaction. (q) A solution of copper(ii) chloride is added to a solution of sodium sulfide. Name the spectator ions in this reaction. (r) Solutions of manganese(ii) sulfate and ammonium sulfide are mixed. List any precipitate that forms during the reaction. 2 Publication No Your Safer Source for Science Supplies 2007 Flinn Scientific, Inc. All Rights Reserved. (800) Fax: (866) P.O. Box 219 Batavia, IL flinn@flinnsci.com

35 (s) Solutions of silver nitrate and sodium chromate are mixed. What is the oxidation number of chromium in the chromate ion? (t) Glacial acetic acid is mixed with liquid methanol (nonaqueous). What type of organic reaction can this be characterized as? (u) Chlorine gas is bubbled into a cold, dilute solution of potassium hydroxide. What element is undergoing oxidation and what element is undergoing reduction? (v) A strip of copper is immersed in a concentrated nitric acid solution. List at least two observations that indicate a chemical reaction is occurring. (w) Hydrogen gas is passed over hot iron(ii) oxide powder. What is the oxidation number of the hydrogen in hydrogen gas? (x) Acidified potassium permanganate is added to a solution of sodium nitrite. Write and balance the oxidation half-reaction for mass and charge. (y) A solution of sodium bromide is added to an acidified solution of potassium bromate. Write and balance the reduction half-reaction for mass and charge. (z) Aluminum metal is added to a solution of copper(ii) chloride. List at least two observations that indicate a chemical reaction is occurring. (aa) Excess chlorine gas is passed over hot iron filings. What type of reaction is occurring? (bb) Magnesium metal is added to nitrogen gas. What is the oxidation number of magnesium before and after the reaction? 3 Publication No Your Safer Source for Science Supplies 2007 Flinn Scientific, Inc. All Rights Reserved. (800) Fax: (866) P.O. Box 219 Batavia, IL flinn@flinnsci.com

36 (cc) Solid lithium hydride is added to distilled water. Is the final solution acidic, basic or neutral? Explain. (dd) Benzene is treated with bromine in the presence of a catalyst. Classify the type of organic reaction that takes place. (ee) Solid lithium oxide is added to excess water. Is the final solution acidic, basic or neutral? Explain. (ff) Solid potassium chlorate is heated in the presence of manganese dioxide as a catalyst. How many moles of reaction products can be produced from one mole of potassium chlorate? (gg) Dilute hydrochloric acid is added to a solution of potassium sulfite. List all spectator ions. (hh) A solution of sulfuric acid is added to a solution of barium hydroxide until the same number of moles of each compound has been added. Is the final solution acidic, basic or neutral? Explain.. (ii) A mixture of solid calcium oxide and solid tetraphosphorus decaoxide is heated. Is the product compound(s) soluble in water? (jj) Sulfur dioxide gas is passed over solid calcium oxide. Name the product compound(s). (kk) Solid zinc sulfide is heated in an excess of oxygen. What change in oxidation state does sulfur undergo in this reaction? (ll) A solution of potassium iodide is added to an acidified solution of potassium dichromate. What is the reducing agent in this reaction? 4 Publication No Your Safer Source for Science Supplies 2007 Flinn Scientific, Inc. All Rights Reserved. (800) Fax: (866) P.O. Box 219 Batavia, IL flinn@flinnsci.com

37 AP Chemistry Chemical Equations Worksheet Answer Key Changes to the AP Chemistry Exam format for 2007 include modification to Question 4 in Section II. Previously, students were asked to write chemical equations for any five of eight given sets of chemical reactions. The new format requires students to write balanced chemical equations showing only the reacting substances (excluding spectator ions) for three different sets of reactants and to answer a short question (requiring no calculator) about each reaction. The questions are intended to test the students understanding of the meaning of the reactions. The College Board has provided only a few examples of the types of questions that might be asked. (Visit the College Board Web site at for examples.) AP Chemistry teachers have asked us if we have any products or worksheets to address this new format. The following list of practice chemical equations is provided as a helpful tool to assist teachers. We have compiled these questions based on our interpretation of the questions on the College Board Web site. Flinn Scientific has no additional information or guidance other than that provided by the College Board on its Web site. In each of the 38 reactions listed below, a representative question about the reaction and the answer to the question are included, along with the balanced chemical equation. We hope that you will find this worksheet helpful in preparing students for the new AP Chemistry chemical equation section. (a) A solution of ammonia is added to a dilute solution of acetic acid. NH 3 + CH 3 COOH NH CH 3 COO (b) Solutions of sodium hydroxide and acetic acid are mixed. OH + CH 3 COOH H 2 O + CH 3 COO (c) Hydrogen sulfide gas is bubbled through excess potassium hydroxide solution. H 2 S + 2OH S 2 + 2H 2 O (d) Solid barium oxide is added to distilled water. BaO + H 2 O Ba OH (e) Solid calcium oxide is exposed to a stream of carbon dioxide gas. Identify the conjugate acid base pairs in this reaction. Answer: NH 3 (base) and NH + 4 (acid) CH 3 COOH (acid) and CH 3 COO (base) Acetic acid is a weak acid. If equal volumes of equal molar solutions are mixed, will the solution ph be >7, 7, or <7? Explain. Answer: >7. The salt of a weak acid (CH 3 COO ) is basic in solution. Write the successive ionization equations for H 2 S. Answer: H 2 S + H 2 O HS + H 3 O + HS + H 2 O S 2 + H 3 O + Is the resulting solution acidic, basic or neutral? Explain. Answer: Basic. Metal oxides form basic compounds in water. What type of reaction has occurred? Answer: A synthesis (or combination) reaction. CaO + CO 2 CaCO 3 (f) Solid dinitrogen pentoxide is added to water. N 2 O 5 + H 2 O 2H + + 2NO 3 (g) Carbon disulfide vapor is burned in excess oxygen. CS 2 + 3O 2 CO 2 + 2SO 2 Is the final solution acidic, basic or neutral? Explain. Answer: Acidic. Nonmetal oxides form acidic compounds in water. What is the oxidizing agent in this reaction? Answer: Oxygen. 5 Publication No Your Safer Source for Science Supplies 2007 Flinn Scientific, Inc. All Rights Reserved. (800) Fax: (866) P.O. Box 219 Batavia, IL flinn@flinnsci.com

38 (h) Lithium metal is burned in air. 4Li + O 2 2Li 2 O (i) A solution of diamminesilver(i) chloride is treated with dilute nitric acid. [Ag(NH 3 ) 2 ] + + Cl + 2H + AgCl + 2NH + 4 (j) A concentrated solution of ammonia is added to a suspension of zinc hydroxide. 4NH 3 + Zn(OH) 2 [Zn(NH 3 ) 4 ] OH (k) Excess concentrated sodium hydroxide solution is added to solid aluminum hydroxide. OH + Al(OH) 3 [Al(OH 4 ] (l) Solid ammonium carbonate is heated. (NH 4 ) 2 CO 3 2NH 3 + CO 2 + H 2 O (m) A solution of hydrogen peroxide is catalytically decomposed. 2H 2 O 2 2H 2 O + O 2 (n) A solution of potassium iodide is electrolyzed. 2I + 2H 2 O I 2 + H 2 + 2OH (o) A solution of copper(ii) sulfate is electrolyzed using inert electrodes. 2Cu H 2 O 2Cu + O 2 + 4H + (p) A solution of ammonium sulfate is added to a saturated solution of barium hydroxide. NH SO Ba OH BaSO 4 + NH 3 + 2H 2 O (q) A solution of copper(ii) chloride is added to a solution of sodium sulfide. Cu 2+ + S 2 CuS (r) Solutions of manganese(ii) sulfate and ammonium sulfide are mixed. Mn 2+ + S 2 MnS Besides combustion, what type of reaction could this be classified as? Answer: The reaction may be classified as both a synthesis and a redox reaction. What is the driving force for this reaction? Answer: Precipitation of silver chloride. What are the possible molecular geometries for the complex ion product? Answer: All [ML 4 ] n+ complex ions have either a tetrahedral or square planar geometry. Name any complex ion formed in the reaction. Answer: Tetrahydroxoaluminate. Classify the type of reaction occurring. Answer: This is a decomposition reaction. Name the element being reduced and the element being oxidized. Answer: Oxygen is being both reduced and oxidized. At which electrode would a gas be released? Answer: Hydrogen gas is released at the cathode (the negative electrode). Is the final solution acidic, basic, or neutral? Answer: Acidic hydrogen ions (H + ) are produced in the reaction. Identify any precipitate formed in the reaction. Answer: Barium sulfate, BaSO 4. Name the spectator ions in this reaction. Answer: The chloride ion, Cl, and the sodium ion, Na +. List any precipitate that forms during the reaction. Answer: Manganese(II) sulfide, MnS. 6 Publication No Your Safer Source for Science Supplies 2007 Flinn Scientific, Inc. All Rights Reserved. (800) Fax: (866) P.O. Box 219 Batavia, IL flinn@flinnsci.com

39 (s) Solutions of silver nitrate and sodium chromate are mixed. 2Ag + + CrO 2 4 Ag 2 CrO 4 (t) Glacial acetic acid is mixed with liquid methanol (nonaqueous). CH 3 COOH + CH 3 OH CH 3 COOCH 3 + H 2 O (u) Chlorine gas is bubbled into a cold, dilute solution of potassium hydroxide. Cl 2 + 2OH ClO + Cl + H 2 O (v) A strip of copper is immersed in a concentrated nitric acid solution. Cu + 4H + + 2NO 3 Cu NO 2 + 2H 2 O (w) Hydrogen gas is passed over hot iron(ii) oxide powder. H 2 + FeO Fe + H 2 O (x) Acidified potassium permanganate is added to a solution of sodium nitrite. 2MnO 4 + 6H + + 5NO 2 2Mn H 2 O + 5NO 3 (y) A solution of sodium bromide is added to an acidified solution of potassium bromate. 5Br + 6H + + BrO 3 3Br 2 + 3H 2 O (z) Aluminum metal is added to a solution of copper(ii) chloride. 2Al + 3Cu 2+ 2Al Cu (aa) Excess chlorine gas is passed over hot iron filings. 3Cl 2 + 2Fe 2FeCl 3 (bb) Magnesium metal is added to nitrogen gas. 3Mg + N 2 Mg 3 N 2 What is the oxidation number of chromium in the chromate ion? Answer: +6. What type of organic reaction can this be characterized as? Answer: An esterification reaction. What element is undergoing oxidation and what element is undergoing reduction? Answer: Chlorine, Cl, is being reduced to 1 (Cl ) and also being oxidized to +1 in ClO. List at least two observations that indicate a chemical reaction is occurring. Answer: Solution color changes from colorless to blue. Bubbles of NO 2 gas are observed at the copper strip. The gas is brown. What is the oxidation number of the hydrogen in hydrogen gas? Answer: Zero the oxidation number of an atom in its elemental form is zero. Write and balance the oxidation half-reaction for mass and charge. Answer: H 2 O + NO 2 NO 3 + 2H + + 2e Write and balance the reduction half-reaction for mass and charge. Answer: 12H + + 2BrO e Br 2 + 6H 2 O List at least two observations that indicate a chemical reaction is occurring. Answer: The aluminum dissolves, a red solid precipitates, the blue color of the solution fades, and the solution temperature increases. What type of reaction is occurring? Answer: A synthesis reaction (or a redox reaction). What is the oxidation number of magnesium before and after the reaction? Answer: Magnesium goes from zero in Mg to +2 in Mg 3 N 2. 7 Publication No Your Safer Source for Science Supplies 2007 Flinn Scientific, Inc. All Rights Reserved. (800) Fax: (866) P.O. Box 219 Batavia, IL flinn@flinnsci.com

40 (cc) Solid lithium hydride is added to distilled water. LiH + H 2 O Li + + OH + H 2 (dd) Benzene is treated with bromine in the presence of a catalyst. Br 2 + C 6 H 6 C 6 H 5 Br + HBr (ee) Solid lithium oxide is added to excess water. Li 2 O + H 2 O 2Li + + 2OH (ff) Solid potassium chlorate is heated in the presence of manganese dioxide as a catalyst. MnO 2KClO 2 3 2KCl + 3O 2 (gg) Dilute hydrochloric acid is added to a solution of potassium sulfite. Is the final solution acidic, basic or neutral? Explain. Answer: Basic. Metallic hydrides react with water to form metallic hydroxides. Classify the type of organic reaction that takes place. Answer: This is a substitution reaction. Is the final solution acidic, basic or neutral? Explain. Answer: Basic. Soluble metal oxides react in water to form bases (metallic hydroxides). How many moles of reaction products can be produced from one mole of potassium chlorate? Answer: 2½ moles. List all spectator ions. Answer: Potassium, K +, and chloride, Cl. 2H + + SO 3 2 H 2 O + SO 2 (hh) A solution of sulfuric acid is added to a solution of barium hydroxide until the same number of moles of each compound has been added. 2H + + SO Ba OH BaSO 4 + 2H 2 O (ii) A mixture of solid calcium oxide and solid tetraphosphorus decaoxide is heated. 6CaO + P 4 O 10 2Ca 3 (PO 4 ) 2 (jj) Sulfur dioxide gas is passed over solid calcium oxide. Is the final solution acidic, basic or neutral? Explain. Answer: Neutral. The neutralization of a strong base [Ba(OH) 2 ] by a strong acid [H 2 SO 4 ] yields a neutral solution. Is the product compound(s) soluble in water? Answer: No. Phosphates other than those of group 1 elements and NH + 4 are insoluble. Name the product compound(s). Answer: Calcium sulfite. SO 2 + CaO CaSO 3 (kk) Solid zinc sulfide is heated in an excess of oxygen. 2ZnS + 3O 2 2ZnO + 2SO 2 (ll) A solution of potassium iodide is added to an acidified solution of potassium dichromate. 6I + 14H + + Cr 2 O 2 7 3I 2 + 2Cr H 2 O What change in oxidation state does sulfur undergo in this reaction? Answer: Sulfur starts out as 2 in ZnS and ends up as +4 in SO 2. The charge is +6. What is the reducing agent in this reaction? Answer: The species that undergoes oxidation, in this case iodide ion, I, is the reducing agent. 8 Publication No Your Safer Source for Science Supplies 2007 Flinn Scientific, Inc. All Rights Reserved. (800) Fax: (866) P.O. Box 219 Batavia, IL flinn@flinnsci.com