# 6.1 Some basic principles

Save this PDF as:

Size: px
Start display at page:

## Transcription

1 Ch 6 Thermochemistry: Energy Flow and Chemical Change 6.1 Forms of Energy and Their Interconversion 6.2 Enthalpy: Heats of Reaction and Chemical Change 6.3 Calorimetry: Laboratory Measurement of Heats of Reaction 6.4 Stoichiometry of Thermochemical Equations 6.5 Hess s Law of Heat Summation 6.6 Standard Heats of Reaction (DH 0 rxn ) 6.1 Some basic principles Energy is the capacity to do work. State A Fuel in the tank change in potential energy EQUALS kinetic energy State B - Fuel burned and exhaust produced A system of fuel and exhaust. A fuel is higher in chemical potential energy than the exhaust. As the fuel burns, some of its potential energy is converted to the kinetic energy of the moving car. 1

2 A chemical system and its surroundings When a chemical reaction takes place, we consider the substancesinvolved. Therefore, the reactants and products are the system. the surroundings the system The system is a part of universe which attention is focused. The surrounding exchanges energy with the system and make up in principle of the rest of the universe. Thermodynamics is the study of heat and its transformations. Thermochemistry is a branch of thermodynamics that deals with the heat involved with chemical and physical changes. Fundamental premise When energy is transferred from one object to another, it appears as work and/or as heat. For our work we must define a system to study; everything else then becomes the surroundings. The system is composed of particles with their own internal energies (E or U). Therefore the system has an internal energy. When a change occurs, the internal energy changes. State properties State property of system is described by giving its composition, temperature, and pressure. State property depends on the state of the system, not on the way the system reaches the state. 2

3 A system transferring energy as heat only. When q is negative (-), the heat flows out of the system into surrounding. When q is positive (+), the heat flows into the system from surrounding. A system losing energy as work only. Zn(s) + 2H + (aq) + 2Cl - (aq) Energy, E DE<0 work done on surroundings H 2 (g) + Zn 2+ (aq) + 2Cl - (aq) When w is negative (-), work done by system. When w is positive (+), work done on system. 3

4 The Sign Conventions* for q, w and DE q + w = DE depends on sizes of q and w depends on sizes of q and w - For q (heat): + means system gains heat, Endothermic; - means system loses heat. Exothermic. For w (work): + means work done on system; -means work done by system. Magnitude of heat English physicist In any process, we are interested in the direction of heat flow and heat magnitude. We express heat, q, in the unit of joules (SI unit) and kilojoules. The joules is named for James Joule who carried out the precise thermodynamic measurement. Traditionally, chemists use the calorie as an energy unit. Calorie is the amount of heat needed to raise 1.00 g water 1 C. 1 cal = J 1 kcal = kj 4

5 6.2 Specific Heat Capacity and Heat Transfer It is important to discuss the magnitude of heat flow in chemical reactions of phase changes. The equation, q = C T, express the relationship between the magnitude of heat flow and temperature change. T = T final -T initial The quantity C is known as heat capacity of the system, having a unit J/ C. Finding the Quantity of Heat from Specific Heat Capacity A layer of copper welded to the bottom of a skillet weighs 125 g. How much heat is needed to raise the temperature of the copper layer from 25 0 C to C? The specific heat capacity (c) of Cu is J/g*K. Given the mass, specific heat capacity and change in temperature, we can use q = c x mass x DT to find the answer. DT in 0 C is the same as for K. q = J g*k x 125 g x (300-25) 0 C = 1.33x10 4 J Coffee-cup calorimeter The heat given out by a reaction is absorbed by water. The mass of water can be determined. The heat capacity of water is 4.18 J/g C. The temperature change can be measured by the thermometer. Heat flow can be calculated for the reaction. Equation, q = mass c T, express the relationship of heat flow and temperature change. The heat flow for the reaction is equal in magnitude, but opposite in sign to that measured by calorimeter 5

6 Determining the Heat of a Reaction You place 50.0 ml of M NaOHin a coffee-cup calorimeter at C and carefully add 25.0 ml of M HCl, also at C. After stirring, the final temperature is C. Calculate q soln (in J). (Assume the total volume is the sum of the individual volumes and that the final solution has the same density and specficheat capacity as water: d = 1.00 g/ml and c = 4.18 J/g*K) 1. We need to determine the limiting reactant from the net ionic equation. 2. The moles of NaOHand HClas well as the total volume can be calculated. 3. From the volume we use density to find the mass of the water formed. 4. At this point, q soln can be calculated using the eqaution, q = mass c T. The heat divided by the M of water will give us the heat per mole of water formed. Determining the Heat of a Reaction HCl(aq) + NaOH(aq) H + (aq) + OH - (aq) H 2 O(l) NaCl(aq) + H 2 O(l) For NaOH M L = mol OH - For HCl M L = mol H + HClis the limiting reactant mol of H 2 O will form during the rxn. total volume after mixing = L L x10 3 ml/l 1.00 g/ml = 75.0 g of water q = mass x specific heat x DT = 75.0 g 4.18 J/g* 0 C ( ) C = 693 J 6

7 Take-home message: The schematic diagram of A bomb calorimeter 6.6 Calorimetery The heat given out by a reaction is absorbed by water. The mass of water can be determined. The heat capacity of water is 4.18 J/g C. The temperature change can be measured by the thermometer. Heat flow can be calculated for the reaction. Equation, q = mass c T, express the relationship of heat flow and temperature change. Insulated outer container Sample dish Burning sample Steel bomb The heat flow for the reaction is equal in magnitude, but opposite in sign to that measured by calorimeter Calculating the Heat of Combustion A manufacturer claims that its new dietetic dessert has fewer than 10 KiloCaloriesper serving. To test the claim, a chemist at the Department of Consumer Affairs places one serving in a bomb calorimeter and burns it in O 2 (the heat capacity of the calorimeter = 8.15 kj/k). The temperature increases C. Is the manufacturer s claim correct? - q sample = q calorimeter q calorimeter kj = heat capacity T = kj/k K = kj kcal = 9.63 Kilocalories 4.18 kj The manufacturer s claim is true. 7

8 6.3 Energy and changes of state A cooling curve for the conversion of gaseous water to ice. Five stages vapor cools, vapor condenses (constant temperature), liquid water cools, liquid water freezes (constant tempterature), solid water cools Quantitative Aspects of Phase Changes Within a phase, a change in heat is accompanied by a change in temperature which is associated with a change in average E k as the most probable speed of the molecules changes. q = (amount)(molar heat capacity)( T) During a phase change, a change in heat occurs at a constant temperature, which is associated with a change in E p, as the average distance between molecules changes. q = (amount)(enthalpy of phase change) 8

9 6.4 The first law of thermodynamics The Meaning of Enthalpy w = -PDV H = E + PV where H is enthalpy D H = DE + P D V q p = D E + P D V = D H D H D E in 1. Reactions that do not involve gases. 2. Reactions in which the number of moles of gas does not change. 3. Reactions in which the number of moles of gas does change but q is >>> P D V. If a chemical reaction occurs under a constant pressure, the difference in enthalpy between product and reactant equals the heat flow for the reaction. Q reaction at a constant pressure = DE + PDV = DH Enthalpy diagrams for exothermic and endothermic processes. CH 4 (g) + 2O 2 (g) CO 2 (g) + 2H 2 O(g) H 2 O(l) H 2 O(g) CH 4 + 2O 2 H initial H 2 O(g) H final Enthalpy, H Enthalpy, H H < 0 heat out H > 0 heat in CO 2 + 2H 2 O H 2 O(l) H final H initial A Exothermic process B Endothermic process q < 0, H product < H reactant q > 0, H product > H reactant 9

10 Drawing Enthalpy Diagrams and Determining the Sign of DH In each of the following cases, determine the sign of H, state whether the reaction is exothermic or endothermic, and draw and enthalpy diagram. (a) H 2 (g) + 1/2O 2 (g) H 2 O(l) kJ (b) 40.7kJ + H 2 O(l) H 2 O(g) Determine whether heat is a reactant or a product. As a reactant, the products are at a higher energy and the reaction is endothermic. The opposite is true for an exothermic reaction (a) The reaction is exothermic. (b) The reaction is endothermic. H 2 (g) + 1/2O 2 (g) (reactants) H 2 O(g) (products) EXOTHERMIC H = kJ ENDOTHERMIC H = +40.7kJ H 2 O(l) (products) H 2 O(l) (reactants) 6.5 Enthalpy change for chemical reactions Thermal chemical reaction shows the enthalpy relationship between reactants and products Rules of thermochemistry The magnitude of H is directly proportional to the amount of reactants or products. H for a reaction is equal in magnitude but opposite in sign for the reverse reaction. The value of for a reaction is the same whether it occurs in onestep or multi-steps. Hess law H = H 1 + H 2 + Some Important Types of Enthalpy Change heat of combustion (DH comb ) heat of formation (DH f ) C 4 H 10 (l) + 13/2O 2 (g) K(s) + 1/2Br 2 (l) KBr(s) 4CO 2 (g) + 5H 2 O(g) heat of fusion (DH fus ) heat of vaporization (DH vap ) NaCl(s) C 6 H 6 (l) C 6 H 6 (g) NaCl(l) 10

11 Using the Heat of Reaction (DH rxn ) to Find Amounts The major source of aluminum in the world is bauxite (mostly aluminum oxide). Its thermal decomposition can be represented by Al 2 O 3 (s) 2Al(s) + 3/2O 2 (g) H rxn = 1676 kj If aluminum is produced this way, how many grams of aluminum can form when 1.000x10 3 kj of heat is transferred? Heat (kj) 1676 kj = 2 mol Al mol of Al X M g of Al 1.000x10 3 kj x 2 mol Al 1676 kj g Al 1 mol Al = g Al 6.7 Hess s Law to Calculate an Unknown H Two gaseous pollutants that form in auto exhaust are CO and NO. An environmental chemist is studying ways to convert them to less harmful gases through the following equation: CO(g) + NO(g) CO 2 (g) + 1/2N 2 (g) D H =? Given the following information, calculate the unknown D H: Equation A: CO(g) + 1/2O 2 (g) CO 2 (g) D H A = kj Equation B: N 2 (g) + O 2 (g) 2NO(g) D H B = kj Equations A and B have to be manipulated by reversal and/or multiplication by factors in order to sum to the first, or target, equation. Multiply Equation B by 1/2 and reverse it. CO(g) + 1/2O 2 (g) CO 2 (g) D H A = kj NO(g) 1/2N 2 (g) + 1/2O 2 (g) D H B = kj CO(g) + NO(g) CO 2 (g) + 1/2N 2 (g) D H rxn = kj 11

12 6.8 Standard enthalpies of Formation Write balanced equations for the formation of 1 mol of the following compounds from their elements in their standard states and include H 0 f. (a) Silver chloride, AgCl, a solid at standard conditions. (b) Calcium carbonate, CaCO 3, a solid at standard conditions. (c) Hydrogen cyanide, HCN, a gas at standard conditions. Use the table of heats of formation for values. (a) Ag(s) + 1/2Cl 2 (g) AgCl(s) (b) Ca(s) + C(graphite) + 3/2O 2 (g) (c) 1/2H 2 (g) + C(graphite) + 1/2N 2 (g) CaCO 3 (s) HCN(g) H 0 f H 0 f H 0 f = kj = kj = 135 kj The general process for determining DH 0 rxn from DH 0 f values. Elements Enthalpy, H Reactants decomposition -DH 0 f formation DH 0 f H initial DH 0 rxn Products H final DH 0 rxn = S mdh 0 f(products) - S ndh 0 f(reactants) 12

13 Calculating the Heat of Reaction from Heats of Formation Nitric acid, whose worldwide annual production is about 8 billion kilograms, is used to make many products, including fertilizer, dyes, and explosives. The first step in the industrial production process is the oxidation of ammonia: 4NH 3 (g) + 5O 2 (g) 4NO(g) + 6H 2 O(g) Calculate H 0 rxn from H 0 f values. Look up the H 0 f values and use Hess s Law to find H rxn. H rxn = Σ m H 0 f (products) - Σ n H0 f (reactants) H rxn = [4( H 0 f NO(g) + 6( H0 f H 2 O(g)] -[4( H0 f NH 3 (g) + 5( H0 f O 2 (g)] = (4 mol)(90.3 kj/mol) + (6 mol)( kj/mol) - [(4 mol)(-45.9 kj/mol) + (5 mol)(0 kj/mol)] H rxn = -906 kj If a chemical reaction occurs under a constant pressure, the difference in enthalpy between product and reactant equals the heat flow for the reaction. Q reaction at a constant pressure = DE + PDV = DH Enthalpy diagrams for exothermic and endothermic processes. CH 4 (g) + 2O 2 (g) CO 2 (g) + 2H 2 O(g) H 2 O(l) H 2 O(g) CH 4 + 2O 2 H initial H 2 O(g) H final Enthalpy, H Enthalpy, H H < 0 heat out H > 0 heat in CO 2 + 2H 2 O H 2 O(l) H final H initial A Exothermic process B Endothermic process q < 0, H product < H reactant q > 0, H product > H reactant 13

14 Drawing Enthalpy Diagrams and Determining the Sign of DH In each of the following cases, determine the sign of H, state whether the reaction is exothermic or endothermic, and draw and enthalpy diagram. (a) H 2 (g) + 1/2O 2 (g) H 2 O(l) kJ (b) 40.7kJ + H 2 O(l) H 2 O(g) Determine whether heat is a reactant or a product. As a reactant, the products are at a higher energy and the reaction is endothermic. The opposite is true for an exothermic reaction (a) The reaction is exothermic. (b) The reaction is endothermic. H 2 (g) + 1/2O 2 (g) (reactants) H 2 O(g) (products) EXOTHERMIC H = kJ ENDOTHERMIC H = +40.7kJ H 2 O(l) (products) H 2 O(l) (reactants) 6.5 Enthalpy change for chemical reactions Thermal chemical reaction shows the enthalpy relationship between reactants and products Rules of thermochemistry The magnitude of H is directly proportional to the amount of reactants or products. H for a reaction is equal in magnitude but opposite in sign for the reverse reaction. The value of for a reaction is the same whether it occurs in onestep or multi-steps. Hess law H = H 1 + H 2 + Some Important Types of Enthalpy Change heat of combustion (DH comb ) heat of formation (DH f ) C 4 H 10 (l) + 13/2O 2 (g) K(s) + 1/2Br 2 (l) KBr(s) 4CO 2 (g) + 5H 2 O(g) heat of fusion (DH fus ) heat of vaporization (DH vap ) NaCl(s) C 6 H 6 (l) C 6 H 6 (g) NaCl(l) 14

15 Using the Heat of Reaction (DH rxn ) to Find Amounts The major source of aluminum in the world is bauxite (mostly aluminum oxide). Its thermal decomposition can be represented by Al 2 O 3 (s) 2Al(s) + 3/2O 2 (g) H rxn = 1676 kj If aluminum is produced this way, how many grams of aluminum can form when 1.000x10 3 kj of heat is transferred? Heat (kj) 1676 kj = 2 mol Al mol of Al X M g of Al 1.000x10 3 kj x 2 mol Al 1676 kj g Al 1 mol Al = g Al 6.7 Hess s Law to Calculate an Unknown H Two gaseous pollutants that form in auto exhaust are CO and NO. An environmental chemist is studying ways to convert them to less harmful gases through the following equation: CO(g) + NO(g) CO 2 (g) + 1/2N 2 (g) D H =? Given the following information, calculate the unknown D H: Equation A: CO(g) + 1/2O 2 (g) CO 2 (g) D H A = kj Equation B: N 2 (g) + O 2 (g) 2NO(g) D H B = kj Equations A and B have to be manipulated by reversal and/or multiplication by factors in order to sum to the first, or target, equation. Multiply Equation B by 1/2 and reverse it. CO(g) + 1/2O 2 (g) CO 2 (g) D H A = kj NO(g) 1/2N 2 (g) + 1/2O 2 (g) D H B = kj CO(g) + NO(g) CO 2 (g) + 1/2N 2 (g) D H rxn = kj 15

16 6.8 Standard enthalpies of Formation Write balanced equations for the formation of 1 mol of the following compounds from their elements in their standard states and include H 0 f. (a) Silver chloride, AgCl, a solid at standard conditions. (b) Calcium carbonate, CaCO 3, a solid at standard conditions. (c) Hydrogen cyanide, HCN, a gas at standard conditions. Use the table of heats of formation for values. (a) Ag(s) + 1/2Cl 2 (g) AgCl(s) (b) Ca(s) + C(graphite) + 3/2O 2 (g) (c) 1/2H 2 (g) + C(graphite) + 1/2N 2 (g) CaCO 3 (s) HCN(g) H 0 f H 0 f H 0 f = kj = kj = 135 kj The general process for determining DH 0 rxn from DH 0 f values. Elements Enthalpy, H Reactants decomposition -DH 0 f formation DH 0 f H initial DH 0 rxn Products H final DH 0 rxn = S mdh 0 f(products) - S ndh 0 f(reactants) 16

17 Calculating the Heat of Reaction from Heats of Formation Nitric acid, whose worldwide annual production is about 8 billion kilograms, is used to make many products, including fertilizer, dyes, and explosives. The first step in the industrial production process is the oxidation of ammonia: 4NH 3 (g) + 5O 2 (g) 4NO(g) + 6H 2 O(g) Calculate H 0 rxn from H 0 f values. Look up the H 0 f values and use Hess s Law to find H rxn. H rxn = Σ m H 0 f (products) - Σ n H0 f (reactants) H rxn = [4( H 0 f NO(g) + 6( H0 f H 2 O(g)] -[4( H0 f NH 3 (g) + 5( H0 f O 2 (g)] = (4 mol)(90.3 kj/mol) + (6 mol)( kj/mol) - [(4 mol)(-45.9 kj/mol) + (5 mol)(0 kj/mol)] H rxn = -906 kj Specific Heat Capacities of Some Elements, Compounds, and Materials Substance Specific Heat Capacity (J/g*K) Substance Specific Heat Capacity (J/g*K) Elements Materials aluminum, Al graphite,c iron, Fe copper, Cu gold, Au wood cement glass granite steel Compounds water, H 2 O(l) ethyl alcohol, C 2 H 5 OH(l) ethylene glycol, (CH 2 OH) 2 (l) carbon tetrachloride, CCl 4 (l)

18 Selected Standard Heats of Formation at 25 0 C(298K) Formula calcium Ca(s) CaO(s) CaCO 3 (s) DH 0 f (kj/mol) carbon C(graphite) 0 C(diamond) 1.9 CO(g) CO 2 (g) CH 4 (g) CH 3 OH(l) HCN(g) 135 CS s (l) 87.9 chlorine Cl(g) Formula Cl 2 (g) HCl(g) hydrogen H(g) H 2 (g) nitrogen N 2 (g) NH 3 (g) NO(g) oxygen O 2 (g) O 3 (g) H 2 O(g) H 2 O(l) DH 0 f (kj/mol) Formula silver Ag(s) AgCl(s) sodium Na(s) Na(g) NaCl(s) DH 0 f (kj/mol) sulfur S 8 (rhombic) 0 S 8 (monoclinic) 2 SO 2 (g) SO 3 (g)

### ENERGY. Thermochemistry. Heat. Temperature & Heat. Thermometers & Temperature. Temperature & Heat. Energy is the capacity to do work.

ENERGY Thermochemistry Energy is the capacity to do work. Chapter 6 Kinetic Energy thermal, mechanical, electrical, sound Potential Energy chemical, gravitational, electrostatic Heat Heat, or thermal energy,

### THERMOCHEMISTRY & DEFINITIONS

THERMOCHEMISTRY & DEFINITIONS Thermochemistry is the study of the study of relationships between chemistry and energy. All chemical changes and many physical changes involve exchange of energy with the

### Name Date Class THERMOCHEMISTRY. SECTION 17.1 THE FLOW OF ENERGY HEAT AND WORK (pages 505 510)

17 THERMOCHEMISTRY SECTION 17.1 THE FLOW OF ENERGY HEAT AND WORK (pages 505 510) This section explains the relationship between energy and heat, and distinguishes between heat capacity and specific heat.

Thermochemistry Reading: Chapter 5 (omit 5.8) As you read ask yourself What is meant by the terms system and surroundings? How are they related to each other? How does energy get transferred between them?

### 3. Of energy, work, enthalpy, and heat, how many are state functions? a) 0 b) 1 c) 2 d) 3 e) 4 ANS: c) 2 PAGE: 6.1, 6.2

1. A gas absorbs 0.0 J of heat and then performs 15.2 J of work. The change in internal energy of the gas is a) 24.8 J b) 14.8 J c) 55.2 J d) 15.2 J ANS: d) 15.2 J PAGE: 6.1 2. Calculate the work for the

### Bomb Calorimetry. Example 4. Energy and Enthalpy

Bomb Calorimetry constant volume often used for combustion reactions heat released by reaction is absorbed by calorimeter contents need heat capacity of calorimeter q cal = q rxn = q bomb + q water Example

### Thermochemical equations allow stoichiometric calculations.

CHEM 1105 THERMOCHEMISTRY 1. Change in Enthalpy ( H) Heat is evolved or absorbed in all chemical reactions. Exothermic reaction: heat evolved - heat flows from reaction mixture to surroundings; products

### Thermodynamics- Chapter 19 Schedule and Notes

Thermodynamics- Chapter 19 Schedule and Notes Date Topics Video cast DUE Assignment during class time One Review of thermodynamics 1_thermo_review AND Review of thermo Wksheet 2.1ch19_intro Optional: 1sc_thermo

### ENTHALPY CHANGES FOR A CHEMICAL REACTION scaling a rxn up or down (proportionality) quantity 1 from rxn heat 1 from Δ r H. = 32.

CHEMISTRY 103 Help Sheet #10 Chapter 4 (Part II); Sections 4.6-4.10 Do the topics appropriate for your lecture Prepared by Dr. Tony Jacob http://www.chem.wisc.edu/areas/clc (Resource page) Nuggets: Enthalpy

### Energy and Chemical Reactions. Characterizing Energy:

Energy and Chemical Reactions Energy: Critical for virtually all aspects of chemistry Defined as: We focus on energy transfer. We observe energy changes in: Heat Transfer: How much energy can a material

### AP* Chemistry THERMOCHEMISTRY

AP* Chemistry THERMOCHEMISTRY Terms for you to learn that will make this unit understandable: Energy (E) the ability to do work or produce heat ; the sum of all potential and kinetic energy in a system

### 87 16 70 20 58 24 44 32 35 40 29 48 (a) graph Y versus X (b) graph Y versus 1/X

HOMEWORK 5A Barometer; Boyle s Law 1. The pressure of the first two gases below is determined with a manometer that is filled with mercury (density = 13.6 g/ml). The pressure of the last two gases below

### Chapter 5. Thermochemistry

Chapter 5. Thermochemistry THERMODYNAMICS - study of energy and its transformations Thermochemistry - study of energy changes associated with chemical reactions Energy - capacity to do work or to transfer

### CHM111 Lab Enthalpy of Hydration of Sodium Acetate Grading Rubric

Name Team Name CHM111 Lab Enthalpy of Hydration of Sodium Acetate Grading Rubric Criteria Points possible Points earned Lab Performance Printed lab handout and rubric was brought to lab 3 Safety and proper

### Unit 5 Practice Test. Name: Class: Date: Multiple Choice Identify the choice that best completes the statement or answers the question.

Name: Class: Date: Unit 5 Practice Test Multiple Choice Identify the choice that best completes the statement or answers the question. 1) The internal energy of a system is always increased by. A) adding

### UNIT 1 THERMOCHEMISTRY

UNIT 1 THERMOCHEMISTRY THERMOCHEMISTRY LEARNING OUTCOMES Students will be expected to: THERMOCHEMISTRY STSE analyse why scientific and technological activities take place in a variety individual and group

### Enthalpy of Reaction and Calorimetry worksheet

Enthalpy of Reaction and Calorimetry worksheet 1. Calcium carbonate decomposes at high temperature to form carbon dioxide and calcium oxide, calculate the enthalpy of reaction. CaCO 3 CO 2 + CaO 2. Carbon

### Problem Solving. Stoichiometry of Gases

Skills Worksheet Problem Solving Stoichiometry of Gases Now that you have worked with relationships among moles, mass, and volumes of gases, you can easily put these to work in stoichiometry calculations.

### SUGGESTION ANSWER SCHEME CHAPTER 8: THERMOCHEMISTRY. 1 (a) Use the data in the table below to answer the following questions:

SUGGESTION ANSWER SCHEME CHAPTER 8: THERMOCHEMISTRY ANSWER SCHEME UPS 2004/2005 SK027 1 (a) Use the data in the table below to answer the following questions: Enthalpy change ΔH (kj/mol) Atomization energy

### Chemistry: Chemical Equations

Chemistry: Chemical Equations Write a balanced chemical equation for each word equation. Include the phase of each substance in the equation. Classify the reaction as synthesis, decomposition, single replacement,

### Mr. Bracken. Multiple Choice Review: Thermochemistry

Mr. Bracken AP Chemistry Name Period Multiple Choice Review: Thermochemistry 1. If this has a negative value for a process, then the process occurs spontaneously. 2. This is a measure of how the disorder

### IB Chemistry. DP Chemistry Review

DP Chemistry Review Topic 1: Quantitative chemistry 1.1 The mole concept and Avogadro s constant Assessment statement Apply the mole concept to substances. Determine the number of particles and the amount

### Calorimeter: A device in which the heat associated with a specific process is measured.

1 CALORIMETRY p. 661-667 (simple), 673-675 (bomb) Calorimeter: A device in which the heat associated with a specific process is measured. There are two basic types of calorimeters: 1. Constant-pressure

### Chapter 20. Thermodynamics p. 811 842. Spontaneity. What have we learned about spontaneity during this course?

Chapter 20 p. 811 842 Spontaneous process: Ex. Nonspontaneous process: Ex. Spontaneity What have we learned about spontaneity during this course? 1) Q vs. K? 2) So.. Spontaneous process occurs when a system

### Chapter 3: Stoichiometry

Chapter 3: Stoichiometry Key Skills: Balance chemical equations Predict the products of simple combination, decomposition, and combustion reactions. Calculate formula weights Convert grams to moles and

### Chapter 3 Mass Relationships in Chemical Reactions

Chapter 3 Mass Relationships in Chemical Reactions Student: 1. An atom of bromine has a mass about four times greater than that of an atom of neon. Which choice makes the correct comparison of the relative

### Calorimetry and Enthalpy. Chapter 5.2

Calorimetry and Enthalpy Chapter 5.2 Heat Capacity Specific heat capacity (c) is the quantity of thermal energy required to raise the temperature of 1g of a substance by 1⁰C The units for specific heat

### Stoichiometry. 1. The total number of moles represented by 20 grams of calcium carbonate is (1) 1; (2) 2; (3) 0.1; (4) 0.2.

Stoichiometry 1 The total number of moles represented by 20 grams of calcium carbonate is (1) 1; (2) 2; (3) 01; (4) 02 2 A 44 gram sample of a hydrate was heated until the water of hydration was driven

### 5.2. Determining Enthalpy of Reaction by Experiment. Specific Heat Capacity. 234 MHR Unit 3 Energy Changes and Rates of Reaction

In this section, you will 5.2 Section Preview/ Specific Expectations determine the heat that is produced by a reaction using a calorimeter, and use the data obtained to calculate the enthalpy change for

### Chemistry B11 Chapter 4 Chemical reactions

Chemistry B11 Chapter 4 Chemical reactions Chemical reactions are classified into five groups: A + B AB Synthesis reactions (Combination) H + O H O AB A + B Decomposition reactions (Analysis) NaCl Na +Cl

### Thermodynamics: First Law, Calorimetry, Enthalpy. Calorimetry. Calorimetry: constant volume. Monday, January 23 CHEM 102H T.

Thermodynamics: First Law, Calorimetry, Enthalpy Monday, January 23 CHEM 102H T. Hughbanks Calorimetry Reactions are usually done at either constant V (in a closed container) or constant P (open to the

### CHM-101-A Exam 2 Version 1 October 10, 2006

CHM-101-A Exam 2 Version 1 1. Which of the following statements is incorrect? A. SF 4 has ¼ as many sulfur atoms as fluorine atoms. B. Ca(NO 3 ) 2 has six times as many oxygen atoms as calcium ions. C.

### 5 Energetics. James Prescott Joule (1818 89) was devoted to making accurate measurements of heat. The SI unit of energy is named after him.

5 Energetics All chemical reactions are accompanied by energy changes. Energy changes are vital. Our body s processes are dependent on the energy changes which occur during respiration, when glucose reacts

### Thermodynamics. S (reactants) S S (products) AP Chemistry. Period Date / / R e v i e w. 1. Consider the first ionization of sulfurous acid:

AP Chemistry Thermodynamics 1. Consider the first ionization of sulfurous acid: H 2SO 3(aq) H + (aq) + HSO 3 - (aq) Certain related thermodynamic data are provided below: H 2SO 3(aq) H + (aq) HSO 3 - (aq)

### Name AP CHEM / / Collected AP Exam Essay Answers for Chapter 16

Name AP CHEM / / Collected AP Exam Essay Answers for Chapter 16 1980 - #7 (a) State the physical significance of entropy. Entropy (S) is a measure of randomness or disorder in a system. (b) From each of

### Spring 2009. kj mol 125 0-229 -92. H f. H rxn = Σ H f (products) - Σ H f (reactants)

Spring 2009 2. The reaction of an elemental halogen with an alkane is a very common reaction. The reaction between chlorine and butane is provided below. (NOTE: Questions a d and f pertain to this reaction.)

### Module 5: Combustion Technology. Lecture 34: Calculation of calorific value of fuels

1 P age Module 5: Combustion Technology Lecture 34: Calculation of calorific value of fuels 2 P age Keywords : Gross calorific value, Net calorific value, enthalpy change, bomb calorimeter 5.3 Calculation

### Sample Exercise 15.1 Writing Equilibrium-Constant Expressions

Sample Exercise 15.1 Writing Equilibrium-Constant Expressions Write the equilibrium expression for K c for the following reactions: Solution Analyze: We are given three equations and are asked to write

### Appendix D. Reaction Stoichiometry D.1 INTRODUCTION

Appendix D Reaction Stoichiometry D.1 INTRODUCTION In Appendix A, the stoichiometry of elements and compounds was presented. There, the relationships among grams, moles and number of atoms and molecules

### Chapter 5 Principles of Chemical Reactivity: Energy and Chemical Reactions

PRACTICING SKILLS Energy Chapter 5 Principles of Chemical Reactivity: 1. To move the lever, one uses mechanical energy. The energy resulting is manifest in electrical energy (which produces light); thermal

### Test Review # 9. Chemistry R: Form TR9.13A

Chemistry R: Form TR9.13A TEST 9 REVIEW Name Date Period Test Review # 9 Collision theory. In order for a reaction to occur, particles of the reactant must collide. Not all collisions cause reactions.

### 0.786 mol carbon dioxide to grams g lithium carbonate to mol

1 2 Convert: 2.54 x 10 22 atoms of Cr to mol 4.32 mol NaCl to grams 0.786 mol carbon dioxide to grams 2.67 g lithium carbonate to mol 1.000 atom of C 12 to grams 3 Convert: 2.54 x 10 22 atoms of Cr to

### Chapter 5. Chemical Reactions and Equations. Introduction. Chapter 5 Topics. 5.1 What is a Chemical Reaction

Introduction Chapter 5 Chemical Reactions and Equations Chemical reactions occur all around us. How do we make sense of these changes? What patterns can we find? 1 2 Copyright The McGraw-Hill Companies,

### DETERMINING THE ENTHALPY OF FORMATION OF CaCO 3

DETERMINING THE ENTHALPY OF FORMATION OF CaCO 3 Standard Enthalpy Change Standard Enthalpy Change for a reaction, symbolized as H 0 298, is defined as The enthalpy change when the molar quantities of reactants

### stoichiometry = the numerical relationships between chemical amounts in a reaction.

1 REACTIONS AND YIELD ANSWERS stoichiometry = the numerical relationships between chemical amounts in a reaction. 2C 8 H 18 (l) + 25O 2 16CO 2 (g) + 18H 2 O(g) From the equation, 16 moles of CO 2 (a greenhouse

### Stoichiometry. 1. The total number of moles represented by 20 grams of calcium carbonate is (1) 1; (2) 2; (3) 0.1; (4) 0.2.

Stoichiometry 1 The total number of moles represented by 20 grams of calcium carbonate is (1) 1; (2) 2; (3) 01; (4) 02 2 A 44 gram sample of a hydrate was heated until the water of hydration was driven

### Standard Free Energies of Formation at 298 K. Average Bond Dissociation Energies at 298 K

1 Thermodynamics There always seems to be at least one free response question that involves thermodynamics. These types of question also show up in the multiple choice questions. G, S, and H. Know what

### Chapter 7: Chemical Equations. Name: Date: Period:

Chapter 7: Chemical Equations Name: Date: Period: 7-1 What is a chemical reaction? Read pages 232-237 a) Explain what a chemical reaction is. b) Distinguish between evidence that suggests a chemical reaction

### Chapter 8 - Chemical Equations and Reactions

Chapter 8 - Chemical Equations and Reactions 8-1 Describing Chemical Reactions I. Introduction A. Reactants 1. Original substances entering into a chemical rxn B. Products 1. The resulting substances from

### The first law: transformation of energy into heat and work. Chemical reactions can be used to provide heat and for doing work.

The first law: transformation of energy into heat and work Chemical reactions can be used to provide heat and for doing work. Compare fuel value of different compounds. What drives these reactions to proceed

### Test 5 Review questions. 1. As ice cools from 273 K to 263 K, the average kinetic energy of its molecules will

Name: Thursday, December 13, 2007 Test 5 Review questions 1. As ice cools from 273 K to 263 K, the average kinetic energy of its molecules will 1. decrease 2. increase 3. remain the same 2. The graph below

### www.chemsheets.co.uk 17-Jul-12 Chemsheets A2 033 1

www.chemsheets.co.uk 17-Jul-12 Chemsheets A2 033 1 AS THERMODYNAMICS REVISION What is enthalpy? It is a measure of the heat content of a substance Enthalpy change ( H) = Change in heat content at constant

### Thermochemistry. r2 d:\files\courses\1110-20\99heat&thermorans.doc. Ron Robertson

Thermochemistry r2 d:\files\courses\1110-20\99heat&thermorans.doc Ron Robertson I. What is Energy? A. Energy is a property of matter that allows work to be done B. Potential and Kinetic Potential energy

### 1. Thermite reaction 2. Enthalpy of reaction, H 3. Heating/cooling curves and changes in state 4. More thermite thermodynamics

Chem 105 Fri 10-23-09 1. Thermite reaction 2. Enthalpy of reaction, H 3. Heating/cooling curves and changes in state 4. More thermite thermodynamics 10/23/2009 1 Please PICK UP your graded EXAM in front.

Chapter 18 Homework Answers 18.22. 18.24. 18.26. a. Since G RT lnk, as long as the temperature remains constant, the value of G also remains constant. b. In this case, G G + RT lnq. Since the reaction

### Chapter 3. Stoichiometry: Ratios of Combination. Insert picture from First page of chapter. Copyright McGraw-Hill 2009 1

Chapter 3 Insert picture from First page of chapter Stoichiometry: Ratios of Combination Copyright McGraw-Hill 2009 1 3.1 Molecular and Formula Masses Molecular mass - (molecular weight) The mass in amu

### Unit 3 Notepack Chapter 7 Chemical Quantities Qualifier for Test

Unit 3 Notepack Chapter 7 Chemical Quantities Qualifier for Test NAME Section 7.1 The Mole: A Measurement of Matter A. What is a mole? 1. Chemistry is a quantitative science. What does this term mean?

### Explorations in Thermodynamics: Calorimetry, Enthalpy & Heats of Reaction

Explorations in Thermodynamics: Calorimetry, Enthalpy & Heats of Reaction Dena K. Leggett, Ph.D. and Jon H. Hardesty, Ph.D. Collin County Community College Dept. of Chemistry 1. Introduction: One of the

### Potassium + Chlorine. K(s) + Cl 2 (g) 2 KCl(s)

Types of Reactions Consider for a moment the number of possible chemical reactions. Because there are millions of chemical compounds, it is logical to expect that there are millions of possible chemical

### Moles. Moles. Moles. Moles. Balancing Eqns. Balancing. Balancing Eqns. Symbols Yields or Produces. Like a recipe:

Like a recipe: Balancing Eqns Reactants Products 2H 2 (g) + O 2 (g) 2H 2 O(l) coefficients subscripts Balancing Eqns Balancing Symbols (s) (l) (aq) (g) or Yields or Produces solid liquid (pure liquid)

### Problem Solving. Percentage Yield

Skills Worksheet Problem Solving Percentage Yield Although we can write perfectly balanced equations to represent perfect reactions, the reactions themselves are often not perfect. A reaction does not

### Chapter 6 Chemical Calculations

Chapter 6 Chemical Calculations 1 Submicroscopic Macroscopic 2 Chapter Outline 1. Formula Masses (Ch 6.1) 2. Percent Composition (supplemental material) 3. The Mole & Avogadro s Number (Ch 6.2) 4. Molar

### AP Practice Questions

1) AP Practice Questions The tables above contain information for determining thermodynamic properties of the reaction below. C 2 H 5 Cl(g) + Cl 2 (g) C 2 H 4 Cl 2 (g) + HCl(g) (a) Calculate ΔH for

### Unit 19 Practice. Name: Class: Date: Multiple Choice Identify the choice that best completes the statement or answers the question.

Name: Class: Date: Unit 19 Practice Multiple Choice Identify the choice that best completes the statement or answers the question. 1) The first law of thermodynamics can be given as. A) E = q + w B) =

### Chem 1A Exam 2 Review Problems

Chem 1A Exam 2 Review Problems 1. At 0.967 atm, the height of mercury in a barometer is 0.735 m. If the mercury were replaced with water, what height of water (in meters) would be supported at this pressure?

### PREPARATION FOR CHEMISTRY LAB: COMBUSTION

1 Name: Lab Instructor: PREPARATION FOR CHEMISTRY LAB: COMBUSTION 1. What is a hydrocarbon? 2. What products form in the complete combustion of a hydrocarbon? 3. Combustion is an exothermic reaction. What

### SUPPLEMENTARY TOPIC 3 ENERGY AND CHEMICAL REACTIONS

SUPPLEMENTARY TOPIC 3 ENERGY AND CHEMICAL REACTIONS Rearranging atoms. In a chemical reaction, bonds between atoms in one or more molecules (reactants) break and new bonds are formed with other atoms to

### Chapter 3 Calculation with Chemical Formulas and Equations

Chapter 3 Calculation with Chemical Formulas and Equations Practical Applications of Chemistry Determining chemical formula of a substance Predicting the amount of substances consumed during a reaction

### CHEM 105 HOUR EXAM III 28-OCT-99. = -163 kj/mole determine H f 0 for Ni(CO) 4 (g) = -260 kj/mole determine H f 0 for Cr(CO) 6 (g)

CHEM 15 HOUR EXAM III 28-OCT-99 NAME (please print) 1. a. given: Ni (s) + 4 CO (g) = Ni(CO) 4 (g) H Rxn = -163 k/mole determine H f for Ni(CO) 4 (g) b. given: Cr (s) + 6 CO (g) = Cr(CO) 6 (g) H Rxn = -26

### W1 WORKSHOP ON STOICHIOMETRY

INTRODUCTION W1 WORKSHOP ON STOICHIOMETRY These notes and exercises are designed to introduce you to the basic concepts required to understand a chemical formula or equation. Relative atomic masses of

### Chapter 5 Chemical Quantities and Reactions. Collection Terms. 5.1 The Mole. A Mole of a Compound. A Mole of Atoms.

Chapter 5 Chemical Quantities and Reactions 5.1 The Mole Collection Terms A collection term states a specific number of items. 1 dozen donuts = 12 donuts 1 ream of paper = 500 sheets 1 case = 24 cans 1

### Name Class Date. Section: Calculating Quantities in Reactions. Complete each statement below by writing the correct term or phrase.

Skills Worksheet Concept Review Section: Calculating Quantities in Reactions Complete each statement below by writing the correct term or phrase. 1. All stoichiometric calculations involving equations

### CHEMICAL REACTIONS. Chemistry 51 Chapter 6

CHEMICAL REACTIONS A chemical reaction is a rearrangement of atoms in which some of the original bonds are broken and new bonds are formed to give different chemical structures. In a chemical reaction,

### 10-Jul-12 Chemsheets AS 029 1

www.cemseets.co.uk 10-Jul-12 Chemsheets AS 029 1 DEFINITIONS What is enthalpy? It is a measure of the heat content of a substance Enthalpy change ( ) = Change in heat content at constant pressure Standard

### Enthalpy of Neutralization. Introduction

Enthalpy of Neutralization Introduction Energy changes always accompany chemical reactions. If energy, in the form of heat, is liberated the reaction is exothermic and if energy is absorbed the reaction

### Chapter 5, Calculations and the Chemical Equation

1. How many iron atoms are present in one mole of iron? Ans. 6.02 1023 atoms 2. How many grams of sulfur are found in 0.150 mol of sulfur? [Use atomic weight: S, 32.06 amu] Ans. 4.81 g 3. How many moles

### Transfer of heat energy often occurs during chemical reactions. A reaction

Chemistry 111 Lab: Thermochemistry Page I-3 THERMOCHEMISTRY Heats of Reaction The Enthalpy of Formation of Magnesium Oxide Transfer of heat energy often occurs during chemical reactions. A reaction may

### Thermochemistry I: Endothermic & Exothermic Reactions

THERMOCHEMISTRY I 77 Thermochemistry I: Endothermic & Exothermic Reactions OBJECTIVES: Learn elementary concepts of calorimetry and thermochemistry Practice techniques of careful temperature, mass, and

### Molecular Formula: Example

Molecular Formula: Example A compound is found to contain 85.63% C and 14.37% H by mass. In another experiment its molar mass is found to be 56.1 g/mol. What is its molecular formula? 1 CHAPTER 3 Chemical

### Sample Exercise 3.1 Interpreting and Balancing Chemical Equations

Sample Exercise 3.1 Interpreting and Balancing Chemical Equations The following diagram represents a chemical reaction in which the red spheres are oxygen atoms and the blue spheres are nitrogen atoms.

### Experiment 17-Chemical Reactions Lab

Since the Middle Ages, when ancient physicians attempted to find a magical substance that would cure all diseases, humans have been fascinated with chemical reactions. In order to effectively describe

### Thermochemistry: Calorimetry and Hess s Law

Thermochemistry: Calorimetry and Hess s Law Some chemical reactions are endothermic and proceed with absorption of heat while others are exothermic and proceed with an evolution of heat. The magnitude

### CHEMICAL EQUILIBRIUM

Chemistry 10 Chapter 14 CHEMICAL EQUILIBRIUM Reactions that can go in both directions are called reversible reactions. These reactions seem to stop before they go to completion. When the rate of the forward

### Name Date Class STOICHIOMETRY. SECTION 12.1 THE ARITHMETIC OF EQUATIONS (pages 353 358)

Name Date Class 1 STOICHIOMETRY SECTION 1.1 THE ARITHMETIC OF EQUATIONS (pages 353 358) This section explains how to calculate the amount of reactants required or product formed in a nonchemical process.

### Unit 8: Chemical Reactions and Equations

1 Chemical Reactions Unit 8: Chemical Reactions and Equations What are chemical reactions and how do they occur? How are chemical reactions classified? How are products of chemical reactions predicted?

### 4. Using the data from Handout 5, what is the standard enthalpy of formation of BaO (s)? What does this mean?

HOMEWORK 3A 1. In each of the following pairs, tell which has the higher entropy. (a) One mole of liquid water or one mole of water vapor (b) One mole of dry ice or one mole of carbon dioxide at 1 atm

### CHAPTER 8 Chemical Equations and Reactions

CHAPTER 8 Chemical Equations and Reactions SECTION 1 Describing Chemical Reactions OBJECTIVES 1. List three observations that suggest that a chemical reaction has taken place. 2. List three requirements

### Mass and Moles of a Substance

Chapter Three Calculations with Chemical Formulas and Equations Mass and Moles of a Substance Chemistry requires a method for determining the numbers of molecules in a given mass of a substance. This allows

### Chemical Equilibrium

Chapter 13 Chemical Equilibrium Equilibrium Physical Equilibrium refers to the equilibrium between two or more states of matter (solid, liquid and gas) A great example of physical equilibrium is shown

### HEAT OF FORMATION OF AMMONIUM NITRATE

303 HEAT OF FORMATION OF AMMONIUM NITRATE OBJECTIVES FOR THE EXPERIMENT The student will be able to do the following: 1. Calculate the change in enthalpy (heat of reaction) using the Law of Hess. 2. Find

### Introductory Chemistry, 3 rd Edition Nivaldo Tro. Roy Kennedy Massachusetts Bay Community College Wellesley Hills, Maqqwertd ygoijpk[l

Introductory Chemistry, 3 rd Edition Nivaldo Tro Quantities in Car an octane and oxygen molecules and carbon dioxide and water Chemical Reactions Roy Kennedy Massachusetts Bay Community College Wellesley

### Chapter 1 The Atomic Nature of Matter

Chapter 1 The Atomic Nature of Matter 6. Substances that cannot be decomposed into two or more simpler substances by chemical means are called a. pure substances. b. compounds. c. molecules. d. elements.

### CP Chemistry Review for Stoichiometry Test

CP Chemistry Review for Stoichiometry Test Stoichiometry Problems (one given reactant): 1. Make sure you have a balanced chemical equation 2. Convert to moles of the known substance. (Use the periodic

### Chapter 4 Notes - Types of Chemical Reactions and Solution Chemistry

AP Chemistry A. Allan Chapter 4 Notes - Types of Chemical Reactions and Solution Chemistry 4.1 Water, the Common Solvent A. Structure of water 1. Oxygen's electronegativity is high (3.5) and hydrogen's

### Chapter 3. Chemical Reactions and Reaction Stoichiometry. Lecture Presentation. James F. Kirby Quinnipiac University Hamden, CT

Lecture Presentation Chapter 3 Chemical Reactions and Reaction James F. Kirby Quinnipiac University Hamden, CT The study of the mass relationships in chemistry Based on the Law of Conservation of Mass

### thermometer as simple as a styrofoam cup and a thermometer. In a calorimeter the reactants are placed into the

Thermochemistry Readin assinment: Chan, Chemistry 10 th edition, pp. 249-258. Goals We will become familiar with the principles of calorimetry in order to determine the heats of reaction for endothermic

### Stoichiometry Review

Stoichiometry Review There are 20 problems in this review set. Answers, including problem set-up, can be found in the second half of this document. 1. N 2 (g) + 3H 2 (g) --------> 2NH 3 (g) a. nitrogen

### Worksheet # 11. 4. When heated, nickel (II) carbonate undergoes a decomposition reaction. Write a balanced equation to describe this reaction

Worksheet # 11 1. A solution of sodium chloride is mixed with a solution of lead (II) nitrate. A precipitate of lead (II) chloride results, leaving a solution of sodium nitrated. Determine the class of