Unit 6: React ions & St oichiom et ry, Chapt er s 11 & 12. Nam e: Period: Description Reaction Types Activty

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1 Unit 6: React ions & St oichiom et ry, Chapt er s 11 & 12 Nam e: Period: Unit Goals- As you work through this unit, you should be able to: 1. Write formula equations from word equations using appropriate symbols. 2. Balance chemical reactions. 3. Classify the equations into the five basic reaction types. 4. Calculate the empirical formula of a compound using experimental reaction data. 5. Understand the different quantitative relationships derived from a balanced equation. 6. Be able to do simple Mass-mole to mole-mass conversions using a balanced equation. 7. Solve stoichiometric problems using mass, volume, and number of particles. 8. Understand the concept of a limiting reagent 9. Identify which reagent is a limiting reagent based on quantities of each reagent and a balanced chemical equation 10. Understand the concept of percent yield and calculate percent yields. Assignments: Activities, Labs & Test Description Reaction Types Activty A1 A2 Water Rockets Activity Mole Ratio & Stoichiometry Lab Making Chalk and Limiting Reagent Lab Unit 6 Test A3 A4 Late Lab Stamp (this stamp means you are not qualified to do lab and test corrections) A5 A6 Readings: Chapter 11: Sections , Chapter 12 Key Terms: empirical formula, word equation, reactant, product, chemical change, physical change, formula equation, product, precipitate, symbols, catalyst, coefficient, conservation of atoms, conservation of mass, combination, decomposition, singlereplacement, double-replacement, combustion, stoichiometry, mole-ratio, limiting reagent, actual yield, theoretical yield Demo s: Calcium carbonate & potassium chlorate decomposition, ethanol & glucose combustion, Calcium Oxide w/ water & sulfur & iron combination, acid base and precipitation of barium sulfate double replacement, silver nitrate w/ copper & lead nitrate w/ zinc single replacement reactions.

2 Ch ap t er 11.1: Chem ical Eq uat ions. What is a chemical equation? Why must chemical equations be balanced? Symbols in a chemical equation and their meanings: *Acids and Bases Chapter 11.2: There are 5 general types of chemical reactions (If A = metal) 4. (If X = nonmetal) 5. (Complete) Define Reactants Define Products A. Write balanced complete equations for each of these chemical reactions. Identify the type of reaction 1. Aluminum metal reacts with oxygen in the air to form aluminum oxide. 2. When solid mercury (II) sulfide is heated with oxygen, liquid mercury metal and gaseous sulfur dioxide are produced.

3 3. Oxygen gas can be made by heating potassium chlorate in the presence of the catalyst manganese dioxide. Potassium chloride is left as a solid residue. 4. Gaseous hydrogen + solid sulfur aqueous hydrosulfuric acid. 5. aqeous iron (III) chloride + aqueous calcium hydroxide solid iron (III) hydroxide + aqueous calcium chloride. 6. Solid Carbon reacts with oxygen from the air gaseous carbon monoxide. 7. Aqueous silver nitrate reacts with solid copper to produce aqueous copper (II) nitrate and solid silver metal. 8. Aluminum metal reacts with oxygen from the air to form solid aluminum oxide. B. COMBINATION REACTIONS 1. Pot assium m et al r eact s w it h Chlorine gas 2. Write the equations for the teacher demonstration: a. C. DECOMPOSITION REACTIONS 1. Silver oxid e d ecom p oses w hen heat ed 2. Write the equations for the teacher demonstration: a.

4 D. SINGLE-REPLACEMENT REACTIONS Will every single replacement reaction work? Yes/No (circle one) Define the activity series, from page 361, and explain what it is used for: 1. Solid m agnesium m et al r eact s w it h aq ueous silver nit r at e 2. Chlorine gas r eact s w it h aq ueo us m agnesium io d id e 3. Write the equations for the teacher demonstration here: a. E. DOUBLE-REPLACEMENT REACTIONS Practice Problems: Write complete balanced equations for the following reactions. 1. Aqueous sodium hydroxide reacts with aqueous iron (III) nitrate (solid Iron (III) hydroxide is formed) (demo) 2. Aqueous sodium hydroxide reacts with hydrochloric acid (demo) 3. Aqueous sodium carbonate reacts with acetic acid to produce three products, one of which is a gas (carbonic acid always decomposes into carbon dioxide and water instantly) (demo). F. COMBUSTION REACTIONS: 1. Methanol, CH 3 OH completely combusts: 2. Write the equations for the teacher demonstration: a The arithmetic of equations A. What is Stoichiometry?

5 B. Let s examine stoichiometry a bit closer by looking at the production of ammonia (NH 3 ) from it s elements: Write the equation below: What kind of information can be derived from this equation? Write sentences to describe the equation - 1. In terms of PARTICLES 2. In terms of MOLES 3. In terms of MASS 4. In terms of VOLUME(for gases only!) C. What was conserved (stayed the same from left to right) in this equation? (2 answers) D. Write the balance equation for the single replacement reaction between Aluminum and Copper (II) Chloride. This is when we saw aluminum appearing to become copper, and the blue solution became clear. Write sentences to describe the equation - 1. In terms of representative PARTICLES 2. In terms of MOLES 3. In terms of MASS 4. In terms of VOLUME(for gases only!)

6 12.2: Chemical Calculations Copy the stoichiometry road map here A. Mole-Mole Calculations 1. What is a mole ratio in a balanced equation? 2. Write a balanced equation for the formation of Ammonia (NH 3 ) from it s elements. 3. Write down all the mole ratios as fractions. Teacher guided example Problem 1: How many moles of ammonia [NH 3(g) ] are produced when 0.60 mol of nitrogen reacts with hydrogen? Teacher guided example Problem 2: How many moles of hydrogen [H 2(g) ] are needed to perfectly react with 1.20 mol of nitrogen gas? Example Problem 3: Write the equation for the formation of aluminum oxide from it s elements.

7 Sample Problems. 1. How many moles of aluminum are needed to form 3.70 moles of aluminum oxide? 2. How many moles of oxygen are required to react completely with 14.8 mole of aluminum? 3. How many moles of aluminum oxide are formed when 0.78 mol of oxygen reacts with aluminum? B. Mass-Mass Calculations: Since you can convert from moles of one substance to moles of another substance using a balanced equation, you can also convert to and from,, & of gasses. We all know how to convert to the mole, and away from the mole based on last chapter. Use the Stoichiometry map to aid in this process. Example Problem: Write the equation for the production of ammonium (NH 3 ) from it s elements: Calculate the mass of water produced by the reaction of 5.4 grams of hydrogen with an excess of oxygen. Example Problems: Aqueous lead (II) nitrate reacts with aqueous potassium iodide to produce the yellow precipitate lead (II) iodide and aqueous potassium nitrate. Write the balanced equation for this reaction. You re a chemical engineer whose job is to produce the maximum amount of the precipitate (used in paints for automobiles) and with the minimum amount of waste possible. What is the most efficient recipe you would use, in terms of grams of both reactants? How many grams of the precipitate would this yield if you completely reacted 5.0 grams of KI? You must produce 1,000 grams of the precipitate in one batch, how many grams of each reactant would you start with? Remember your job depends on not wasting any reactant!

8 C. Other Stoichiometric Calculations Example Problem: How many molecules of oxygen are produced when a sample of 29.2 grams of water is decomposed by electrolysis? Example Problem: How many molecules of oxygen are produced by the decomposition of 6.54 grams of potassium chlorate? Potassium chloride is also produced. Example Problem: Assuming STP, how many liters of oxygen gas are needed to produce 19.8 L sulfur trioxide according to this balanced equation? 2SO 2 (g) + O 2 (g) 2SO 3 (g) Example Problem: Nitrogen monoxide and oxygen gas combine to form the brown gas nitrogen dioxide. How many milliliters of nitrogen dioxide are produced when 3.4 milliliters of oxygen react with an excess of nitrogen monoxide? Assume STP conditions. Section 12.3 Limiting and Excess Reagents A. In a chemical reaction, an quantity of any reactant will limit the amount of that forms. 1. Write the equation for the production of water: This represents the most efficient recipe that a chemist can follow. What if this equation is run at any other mole ratio? Define Limiting Reagent- Define Excess Reagent- If you react 5 moles of hydrogen gas with 5 moles of oxygen gas, which is limiting and which is excess. Prove it showing your work.

9 2. Example Problem: Sodium chloride can be prepared by the reaction of sodium with chlorine gas according to this equation: Suppose that 6.7 mol of sodium reacts with 3.2 mol chlorine. a. What is the limiting reagent? b. How many moles of sodium chloride are produced 3. Example Problem: Write the equation for the complete combustion of ethene, C 2 H 4 : If 2.7 mol of ethene is reacted with 6.3 mole of oxygen: a. what is the limiting reagent? b. calculate the moles of water produced 4. Example Problem: Write the equation for the incomplete combustion of ethene. If 2.7 mole of ethene is reacted with 6.3 mole of oxygen: a. what is the limiting reagent?

10 b. calculate the moles of water produced 5. Example Problem: When copper reacts with sulfur, solid copper (I) sulfide is produced. Write this combination reaction. a. What is the limiting reagent when 80.0 grams of copper reacts with 25.0 grams of sulfur? b. What is the maximum number of grams of product that can be formed? 6. Example Problem: Hydrogen gas can be produced in the lab by reaction of magnesium metal with hydrochloric acid. Write the COMPLETE balanced equation on the top of the next page: a. Identify the limiting reagent when 6 grams of HCl reacts with 5 grams of Mg. b. How many grams of hydrogen can be produced?

11 Section 12.3 Percent Yield A. Calculating the Percent Yield 1. Define Yield This is the amount of that could be formed during a reaction based on calculations. 2. Define Yield In contrast to Theoretical Yield, yield is the amount of that actually during a. 3. Define Yield Is the ration of to expressed as a. 4. Note that in order to calculate the theoretical amount produced, you must first identify the so you can find the reactant that limits the amount of product that can actually. Example Problem Calcium carbonate is decomposed by heating. Write the balanced equation for this reaction. a. What is the theoretical yield of CaO if 24.8 grams CaCO 3 is heated? b. What is the percent yield if 13.1 grams CaO is produced? Example Problem When 101 grams of solid iron (III) oxide reacts with 62.3 L of carbon monoxide gas, 40.3 grams of solid iron is produced. The other product in the reaction is carbon dioxide gas. Write the balanced equation here: What is the percent yield of this reaction? -1 st, find the limiting reagent so you know how much product theoretically is produced -2 nd, Calcualte % yeild

12 Example Problem If 50.0 grams of silicon dioxide is heated with 35.0 grams of carbon, 27.9 grams of silicon carbide, SiC, is produced. The other product is carbon monoxide gas. Write the balanced equation here: What is the percent yield of this reaction? -1 st, find the limiting reagent so you know how much product theoretically is produced -2 nd, Calcualte % yeild -3 rd, how much excess reagent is left over?