SUPPLEMENTARY TOPIC 3 ENERGY AND CHEMICAL REACTIONS
|
|
- Franklin Powers
- 7 years ago
- Views:
Transcription
1 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 produce different molecules (products). These reactions can only occur if the molecules involved collide with sufficient energy to allow the bonds to break, a process which always requires energy input. When the new bonds form as a result of the collision, energy is released. Overall, there may be a nett release of energy (EXOTHERMIC reaction) or there may be a nett requirement for energy to be supplied (ENDOTHERMIC reaction). The heat supplied by burning gas is an example of an exothermic reaction, while the production of the metal iron from its ore, iron oxide, is endothermic, the heat energy required being supplied in a blast furnace. During chemical reactions, although bonds are broken and new bonds are formed, the same atoms remain in the same quantities after the reaction as there were before. It is a fundamental law of chemistry that atoms are not created or destroyed during chemical change. For this reason, whenever a balanced chemical equation is written for a reaction, all atoms which appear on the reactants side must also appear on the products side of that equation. The following equation shows the formation of water from its elements, and includes structural formulas to emphasise the bonds broken and formed. H H + O=O + H H H O H + H O H This would of course usually be written as 2H 2 + O 2 2H2O. Energy changes. All molecules have energy stored in their chemical bonds. Some of this energy can be released (mostly as heat) when they react to form molecules which have less energy than the reactants, the reaction being classed as EXOTHERMIC. Alternatively, in an ENDOTHERMIC reaction, additional energy is supplied to the reactants so that the products finish up with more energy stored in their chemical bonds than the reactants had originally. The total energy stored in a collection of molecules is called the ENTHALPY of that substance (H), and for the overall reaction, the difference (enthalpy of products enthalpy of reactants) is the energy released or taken up. This enthalpy difference is given the symbol ÄH. The enthalpy change for a chemical reaction can be measured experimentally by observing the temperature change (increase or decrease) when the reaction is carried out in a thermally insulated container basically similar to a thermos flask. Such a container is called a CALORIMETER. As an example, the burning of carbon in oxygen releases 394 kj for each mole of carbon (12.01 g) used. This is represented by the THERMODYNAMIC EQUATION which shows the enthalpy change as well as the reactants and products and their physical states. C(s) + O 2(g) CO 2(g) ÄH = 394 kj/mol The sign indicates the energy is released. For an endothermic reaction, a + sign is used for ÄH. Thus for the electrolysis of water, an endothermic process, the corresponding thermodynamic equation is ST3-1
2 ST3-2 H2O(l) H 2(g) + ½O 2(g) ÄH = +285 kj/mol This reaction can be reversed by burning hydrogen in oxygen to produce water as a vapour which then condenses to form liquid water. The energy released by this exothermic reaction is numerically exactly the same as the energy supplied (per mole of water) in the electrolysis reaction, but with the sign reversed. Thus the process could be represented by the following thermodynamic equation H 2(g) + ½O 2(g) H2O(l) ÄH = 285 kj/mol Consider another example - the burning of methane, the main component of natural gas, to form gaseous water and carbon dioxide. This exothermic reaction releases 889 kj from each mole of methane used so the thermodynamic equation for the reaction is CH 4(g) + 4H 2(g) CO 2(g) + H2O(g) ÄH = 889 kj/mol Energy units. There are various units used to express an amount of energy. In science, the normal unit used is the joule, abbreviated as J. Note that energy and work units are identical as these two are interchangeable - energy is expended doing work or work can be harnessed to produce energy. The use of kj per mole in the above thermodynamic equations can be somewhat confusing until one realises that the per mole part merely indicates that all quantities are expressed in moles. The actual numbers of moles of each constituent is given by the stoichiometric coefficients as written in the equation. 1 It is customary to write the per mole as mol " using the exponential notation. Thus while ÄH for the reaction equation H 2(g) + ½O 2(g) H2O(l) 1 ÄH = 285 kj mol shows that 285 kj is released for the formation of 1 mole of H2O, ÄH for the reaction equation 1 2H 2(g) + O 2(g) 2H2O(l) ÄH = 570 kj mol shows that 2 ( 285) = 570 kj is released for the formation of 2 moles of H2O. Consequently a ÄH value for a reaction must be accompanied by the equation to which it refers. Check your understanding of this section. (a) Write a thermodynamic equation for the combustion of methane (natural gas). A typical household uses 100 megajoules each quarter on average. Calculate what mass of methane this would correspond to having been burnt. 6 (1 megajoule = 10 joules) 1 (b) Given H (g) + Cl (g) 2HCl(g) ÄH = 184 kj mol, 2 2 calculate ÄH for the reaction / H (g) + / Cl (g) HCl(g)
3 ST3-3 Activation energy: why you need a match to light the gas? Consider the reaction of hydrogen with oxygen again. A mixture of these two gases in a balloon remains indefinitely without reacting. However, application of a small amount of energy such as from a spark or a match causes the reaction to proceed instantaneously to completion, releasing the 285 kj of energy for every mole (2.0 g) of H 2 reacting. [This is the fuel mixture that was used in the Space Shuttle.] The reaction could not start without the heat supplied by the match because there is an "energy barrier" between the reactants and products. Recall that energy is always needed to break bonds, and that before any energy can be obtained through the formation of new bonds, at least some of the old bonds must be broken. This energy barrier is called the ACTIVATION ENERGY of the reaction. Apparently, in the original mixture, not enough of the hydrogen and oxygen molecules have sufficient energy when they collide for reaction to occur no matter how long one waits. By supplying the additional energy from the match to relatively few molecules, they are then able to react and in the process release energy to the remaining molecules, thereby providing the activation energy for all the remaining molecules to react, as the reaction is exothermic. This can be illustrated on an energy diagram. Check your understanding of this section. The process of charging a car battery involves some electrolysis of the sulfuric acid / water mixture in the battery. Why should one not use a match to inspect the electrolyte level in the battery? Catalysts. Catalysts are substances which, when present, reduce the activation energy for a given reaction by providing a different, lower-energy pathway, thereby causing the reaction to proceed faster. Catalysts are not consumed in the reaction, and do not give a greater final yield of products - they only make the reaction faster, thereby increasing the yield obtained in a given time. The following diagram represents the enthalpy change for a reaction with and without a catalyst present.
4 ST3-4 There are many different types of catalysts. Some are simply metals which have a suitable surface on which to promote a particular reaction - eg platinum gauze can catalyse the reaction between hydrogen and oxygen. All modern motor cars have a canister containing metal catalysts in their exhaust systems to catalyse the reaction of unburnt hydrocarbons to carbon dioxide and water. The catalyst used would become "poisoned" if any lead came in contact with it, and this was the original reason why unleaded fuel was introduced, although later concern about lead levels in blood may cause one to believe that this was the reason. As replacement canisters of catalyst for cars cost about $500, it was most important not to ever allow leaded fuel to enter the petrol tank of a car requiring unleaded fuel. The elimination of leaded fuel has removed this risk. Many industrial processes would not be feasible without the use of catalysts which allow greater yields in a given amount of time and/or allow a lower temperature to be used, thereby saving on fuel costs. The Haber synthesis, a method whereby nitrogen and hydrogen are combined to form ammonia, is responsible for about half of the nitrogen fixed on earth. This synthesis would not be feasible without the catalyst used in the industrial process. The search is currently under way to find catalysts that can lead to the commercial production of hydrogen economically enough to become a fuel for motor vehicles. Energy content of some common fuels. The following illustration shows the energy supplied by complete combustion of some common fuels. The units used are kilojoules per gram of the fuel. The chemical energy released from the fuel can be harnessed for other purposes - e.g. to do work such as in an internal combustion engine or to generate electricity which in turn can be used to do work via an electric motor. Note that the process of conversion of the original energy from the fuel into useful work is seldom even 50% efficient.
5 ST3-5 Energy and living systems. The same laws governing energy and work apply equally well to living systems (in vivo) as they do to chemical changes in test tubes (in vitro). Apart from nuclear energy, earth is ultimately dependent on energy from the sun in the form of electromagnetic radiation (EMR) in the infra-red, visible and ultra-violet frequencies. The energy carried by EMR is converted to chemical energy stored in the bonds of CARBOHYDRATES by plants through the process of PHOTOSYNTHESIS, in particular via formation of the monosaccharide called GLUCOSE as shown in the following equation. 6CO 2(g) + 6H2O(l) C6H12O 6(s) + 6O 2(g) ÄH = kj mol 1 Glucose and other simple carbohydrates are combined to form polymers called POLYSACCHARIDES, such as CELLULOSE and STARCH. n C6H12O 6 (C6H10O 5) n where n is > 1000 Cellulose provides structural strength for plant cells and starch provides a reserve store of glucose for energy requirements. The energy stored in the chemical bonds of oil, coal and natural gas represents reserves of solar energy from millions of years past, laid down at a time when the climate favoured prolific plant growth. Objectives of this Topic. After studying this Topic, you should have achieved the following goals: 1. Recognise that energy is stored in chemical bonds. 2. Know that when chemical reactions occur, energy is required to break bonds and is released when new bonds form, and that there will be an overall energy change equal to the difference between the energy stored in the bonds of the products and reactants.
6 ST Know that both endothermic and exothermic reactions require some energy input to initiate them - called the activation energy for that reaction. 4. Understand that the energy change for a reaction proceeding one way is identical, but of opposite sign, to the energy change for the same reaction in reverse. 5. Be able to write a thermodynamic equation and interpret the ÄH data associated with it. 6. Understand the role of catalysts in lowering the activation energy barrier by providing an alternative pathway for the reaction. 7. Know that energy can be obtained from fuels and foods substances which undergo exothermic reactions and that the energy released can in part be made to do work or support living systems. SUMMARY. Chemical reactions involve the breaking of existing bonds in the reactants and the forming of new bonds in the products. These changes are accompanied by energy changes - exothermic if there is a nett release of energy and endothermic if there is a nett gain of energy by the components of the reaction. The total energy stored in a collection of molecules is called its enthalpy and is given the symbol H. When a reaction occurs, the total energy change is represented as ÄH. If the reaction is exothermic, the enthalpy change is given a negative sign while if the reaction is endothermic, absorbing energy, the enthalpy change is given a positive sign. The energy change for a reaction going in the forward direction has the same magnitude as that for the reaction going in the reverse direction. An equation which shows the reactants and their physical states as well as the accompanying enthalpy change is called a thermodynamic equation. Reacting molecules must collide with enough energy to break bonds (always an endothermic process) before any energy can be obtained from the formation of new bonds (always exothermic). Consequently every reaction always has an activation energy requirement which must be supplied before the reaction can proceed. This activation energy barrier can be lowered by substances called catalysts which provide an alternative reaction pathway. They are not consumed in the reaction but merely allow it to proceed much more rapidly. Energy derivable from fuel and foods can be used to do work or to allow living systems to function.
7 XVI - 7 TUTORIAL QUESTIONS - SUPPLEMENTARY TOPIC What is meant by the terms "exothermic reaction" and "endothermic reaction"? Give two examples of each. 2. What is the reason why chemical reactions are usually accompanied by gain or loss of heat? 3. Why is it that a reaction which is exothermic such as the combustion of hydrogen gas still requires heat to be supplied before it starts? 4. Utilisation of glucose as a food releases 2807 kj of energy per mole of glucose. Where did the energy to make glucose originate? What happens to the energy released when glucose is utilised? 5. Explain the role of a catalyst. What are the characteristics of catalysts? 6. The Haber synthesis of ammonia produces half of all the nitrogen that is fixed on earth. This reaction combines nitrogen gas and hydrogen gas at high pressure and temperature using a catalyst to achieve large yields economically. Given that for the reaction N (g) + 3H (g) 2NH (g) ÄH = 91.8 kj mol calculate the amount of energy released in the production of 100 g of ammonia. ANSWERS TO TUTORIAL SUPPLEMENTARY TOPIC Exothermic reactions are those that liberate heat while endothermic reactions absorb heat as a result of the reaction occurring. Burning fuels such as methane (natural gas) or petrol are exothermic. Endothermic reactions include the smelting of metal ores such as iron oxide to form the metal. Another example is the formation of carbohydrates by plants using solar energy to provide the required energy. 2. There is usually a difference between the energy stored in the bonds of the reactants and the products. This energy difference is made apparent by the gain or loss of heat during the reaction. 3. To initiate reactions requires some energy to be supplied because the first step involves the breaking of bonds in the reactants, a process that always needs energy input. Once even a small number of bonds have been broken, the energy released from the formation of new bonds may sustain the reaction so continued heating may not be required. For example, a mixture of hydrogen and oxygen gases will not combine unless a spark or similar small amount of heat is supplied and then the mixture explodes instantaneously. The energy required to make a reaction proceed is called its activation energy.
8 XVI The chemical energy stored in the bonds of glucose originated as energy from the sun. Glucose undergoes a series of reactions in cells of the body, ultimately being transformed into water and carbon dioxide and releasing energy in the process. The energy released is used to drive chemical reactions required for processes involved in the metabolism within living cells. 5. Catalysts are substances that enable the activation energy of a reaction to be lowered by using a different pathway between the reactants and the products. Catalysts are not consumed in the reaction and do not increase the yield but speed it up, allowing more product to be obtained in a shorter time and often with the need for less heat to be supplied because the activation energy is smaller. 6. The thermodynamic equation for the reaction, N 2(g) + 3H 2(g) 2NH 3(g) ÄH = 91.8 kj mol 1 shows that the production of 2 moles of ammonia releases 91.8 kj of energy. Molar mass of NH 3 = g mol 1 2 moles of NH 3 has a mass = = g and releases 91.8 kj of energy. production of 100 g of NH 3 releases / kj = 269 kj of energy.
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
More informationChemistry 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
More informationTest 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.
More informationChemical Reactions Practice Test
Chemical Reactions Practice Test Chapter 2 Name Date Hour _ Multiple Choice Identify the choice that best completes the statement or answers the question. 1. The only sure evidence for a chemical reaction
More informationEnergy 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
More informationIB Chemistry 1 Mole. One atom of C-12 has a mass of 12 amu. One mole of C-12 has a mass of 12 g. Grams we can use more easily.
The Mole Atomic mass units and atoms are not convenient units to work with. The concept of the mole was invented. This was the number of atoms of carbon-12 that were needed to make 12 g of carbon. 1 mole
More informationCHEMISTRY STANDARDS BASED RUBRIC ATOMIC STRUCTURE AND BONDING
CHEMISTRY STANDARDS BASED RUBRIC ATOMIC STRUCTURE AND BONDING Essential Standard: STUDENTS WILL UNDERSTAND THAT THE PROPERTIES OF MATTER AND THEIR INTERACTIONS ARE A CONSEQUENCE OF THE STRUCTURE OF MATTER,
More informationCOMBUSTION. In order to operate a heat engine we need a hot source together with a cold sink
COMBUSTION In order to operate a heat engine we need a hot source together with a cold sink Occasionally these occur together in nature eg:- geothermal sites or solar powered engines, but usually the heat
More informationDETERMINING 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
More informationName 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.
More informationBalancing chemical reaction equations (stoichiometry)
Balancing chemical reaction equations (stoichiometry) This worksheet and all related files are licensed under the Creative Commons Attribution License, version 1.0. To view a copy of this license, visit
More informationIntroductory 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
More informationChem 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?
More informationModule 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
More informationIB 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
More informationBomb 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
More informationChapter 7: Chemical Energy
Chapter 7: Chemical Energy Goals of Period 7 Section 7.1: To describe atoms, chemical elements and compounds Section 7.2: To discuss the electromagnetic force and physical changes Section 7.3: To illustrate
More informationThe energy level diagram for this reaction is shown below.
Q. Methanol can be made when methane reacts with oxygen. (a) The energy level diagram for this reaction is shown below. (i) What is the energy change represented by A? () (ii) Use the energy level diagram
More informationThermochemical 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
More information1. What is the molecular formula of a compound with the empirical formula PO and a gram-molecular mass of 284 grams?
Name: Tuesday, May 20, 2008 1. What is the molecular formula of a compound with the empirical formula PO and a gram-molecular mass of 284 grams? 2 5 1. P2O 5 3. P10O4 2. P5O 2 4. P4O10 2. Which substance
More information87 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
More informationChemical Equations & Stoichiometry
Chemical Equations & Stoichiometry Chapter Goals Balance equations for simple chemical reactions. Perform stoichiometry calculations using balanced chemical equations. Understand the meaning of the term
More informationUNIT 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
More informationModule 5: Combustion Technology. Lecture 33: Combustion air calculation
1 P age Module 5: Combustion Technology Lecture 33: Combustion air calculation 2 P age Keywords: Heat of combustion, stoichiometric air, excess air, natural gas combustion Combustion air calculation The
More information7-5.5. Translate chemical symbols and the chemical formulas of common substances to show the component parts of the substances including:
7-5.5 Translate chemical symbols and the chemical formulas of common substances to show the component parts of the substances including: NaCl [salt], H 2 O [water], C 6 H 12 O 6 [simple sugar], O 2 [oxygen
More informationLecture 35: Atmosphere in Furnaces
Lecture 35: Atmosphere in Furnaces Contents: Selection of atmosphere: Gases and their behavior: Prepared atmospheres Protective atmospheres applications Atmosphere volume requirements Atmosphere sensors
More informationSample Problem: STOICHIOMETRY and percent yield calculations. How much H 2 O will be formed if 454 g of. decomposes? NH 4 NO 3 N 2 O + 2 H 2 O
STOICHIOMETRY and percent yield calculations 1 Steps for solving Stoichiometric Problems 2 Step 1 Write the balanced equation for the reaction. Step 2 Identify your known and unknown quantities. Step 3
More informationThe 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
More informationThermodynamics Worksheet I also highly recommend Worksheets 13 and 14 in the Lab Manual
Thermodynamics Worksheet I also highly recommend Worksheets 13 and 14 in the Lab Manual 1. Predict the sign of entropy change in the following processes a) The process of carbonating water to make a soda
More informationCalculations with Chemical Formulas and Equations
Chapter 3 Calculations with Chemical Formulas and Equations Concept Check 3.1 You have 1.5 moles of tricycles. a. How many moles of seats do you have? b. How many moles of tires do you have? c. How could
More informationChapter 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
More informationEquilibria Involving Acids & Bases
Week 9 Equilibria Involving Acids & Bases Acidic and basic solutions Self-ionisation of water Through reaction with itself: The concentration of water in aqueous solutions is virtually constant at about
More informationINTI COLLEGE MALAYSIA A? LEVEL PROGRAMME CHM 111: CHEMISTRY MOCK EXAMINATION: DECEMBER 2000 SESSION. 37 74 20 40 60 80 m/e
CHM111(M)/Page 1 of 5 INTI COLLEGE MALAYSIA A? LEVEL PROGRAMME CHM 111: CHEMISTRY MOCK EXAMINATION: DECEMBER 2000 SESSION SECTION A Answer ALL EIGHT questions. (52 marks) 1. The following is the mass spectrum
More informationTHE MOLE / COUNTING IN CHEMISTRY
1 THE MOLE / COUNTING IN CHEMISTRY ***A mole is 6.0 x 10 items.*** 1 mole = 6.0 x 10 items 1 mole = 60, 00, 000, 000, 000, 000, 000, 000 items Analogy #1 1 dozen = 1 items 18 eggs = 1.5 dz. - to convert
More informationHow To Calculate Mass In Chemical Reactions
We have used the mole concept to calculate mass relationships in chemical formulas Molar mass of ethanol (C 2 H 5 OH)? Molar mass = 2 x 12.011 + 6 x 1.008 + 1 x15.999 = 46.069 g/mol Mass percentage of
More informationChemical reactions allow living things to grow, develop, reproduce, and adapt.
Section 2: Chemical reactions allow living things to grow, develop, reproduce, and adapt. K What I Know W What I Want to Find Out L What I Learned Essential Questions What are the parts of a chemical reaction?
More informationUnit 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
More informationChapter Three: STOICHIOMETRY
p70 Chapter Three: STOICHIOMETRY Contents p76 Stoichiometry - The study of quantities of materials consumed and produced in chemical reactions. p70 3-1 Counting by Weighing 3-2 Atomic Masses p78 Mass Mass
More informationComposition of the Atmosphere. Outline Atmospheric Composition Nitrogen and Oxygen Lightning Homework
Molecules of the Atmosphere The present atmosphere consists mainly of molecular nitrogen (N2) and molecular oxygen (O2) but it has dramatically changed in composition from the beginning of the solar system.
More information11-1 Stoichiometry. Represents
11-1 Stoichiometry What is stoichiometry? Calculations that relate the quantities of substances. It is the study of quantitative (measurable amounts) relationships in chemical reactions and equations.
More informationUnit 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) =
More informationEnthalpy 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
More informationChemical Formulas, Equations, and Reactions Test Pre-AP Write all answers on your answer document.
Name: Period: Chemical Formulas, Equations, and Reactions Test Pre-AP Write all answers on your answer document. 1. Which of the following is a NOT a physical property of hydrogen? A. It is gas C. It is
More informationChapter 2. The Chemistry of Life Worksheets
Chapter 2 The Chemistry of Life Worksheets (Opening image courtesy of David Iberri, http://en.wikipedia.org/wiki/file:camkii.png, and under the Creative Commons license CC-BY-SA 3.0.) Lesson 2.1: Matter
More informationChapter 4: Chemical and Solution Stoichiometry
Chapter 4: Chemical and Solution Stoichiometry (Sections 4.1-4.4) 1 Reaction Stoichiometry The coefficients in a balanced chemical equation specify the relative amounts in moles of each of the substances
More informationChapter 4. Chemical Energy
hapter 4 hemical Energy Perhaps the most convenient form in which to store energy is chemical energy. The foods we eat, combined with the oxygen we breathe, store energy that our bodies extract and convert
More information1. The graph below represents the potential energy changes that occur in a chemical reaction. Which letter represents the activated complex?
1. The graph below represents the potential energy changes that occur in a chemical reaction. Which letter represents the activated complex? 4. According to the potential energy diagram shown above, the
More informationChapter 6 Thermodynamics: The First Law
Key Concepts 6.1 Systems Chapter 6 Thermodynamics: The First Law Systems, States, and Energy (Sections 6.1 6.8) thermodynamics, statistical thermodynamics, system, surroundings, open system, closed system,
More informationProblem 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.
More informationChemical Calculations: Formula Masses, Moles, and Chemical Equations
Chemical Calculations: Formula Masses, Moles, and Chemical Equations Atomic Mass & Formula Mass Recall from Chapter Three that the average mass of an atom of a given element can be found on the periodic
More informationIndiana's Academic Standards 2010 ICP Indiana's Academic Standards 2016 ICP. map) that describe the relationship acceleration, velocity and distance.
.1.1 Measure the motion of objects to understand.1.1 Develop graphical, the relationships among distance, velocity and mathematical, and pictorial acceleration. Develop deeper understanding through representations
More informationName: Teacher: Pd. Date:
Name: Teacher: Pd. Date: STAAR Tutorial : Energy and Matter: Elements, Compounds, and Chemical Equations: 6.5C Differentiate between elements and compounds on the most basic level. 8.5F Recognize whether
More informationChapter 2: Forms of Energy
Chapter 2: Forms of Energy Goals of Period 2 Section 2.1: To describe the forms of energy Section 2.2: To illustrate conversions from one form of energy to another Section 2.3 To describe energy storage
More informationCalculating Atoms, Ions, or Molecules Using Moles
TEKS REVIEW 8B Calculating Atoms, Ions, or Molecules Using Moles TEKS 8B READINESS Use the mole concept to calculate the number of atoms, ions, or molecules in a sample TEKS_TXT of material. Vocabulary
More information20.2 Chemical Equations
All of the chemical changes you observed in the last Investigation were the result of chemical reactions. A chemical reaction involves a rearrangement of atoms in one or more reactants to form one or more
More informationChemical Calculations: The Mole Concept and Chemical Formulas. AW Atomic weight (mass of the atom of an element) was determined by relative weights.
1 Introduction to Chemistry Atomic Weights (Definitions) Chemical Calculations: The Mole Concept and Chemical Formulas AW Atomic weight (mass of the atom of an element) was determined by relative weights.
More informationpencil. Vocabulary: 1. Reactant 2. Product 3. Activation energy 4. Catalyst 5. substrate 6. Chemical reaction Keep your textbooks when you are done
Objectives Students will explore the importance of chemical reactions in biology Students will discuss the role of enzymes as catalysts in biological reactions. Students will analyze graphs showing how
More informationAS1 MOLES. oxygen molecules have the formula O 2 the relative mass will be 2 x 16 = 32 so the molar mass will be 32g mol -1
Moles 1 MOLES The mole the standard unit of amount of a substance the number of particles in a mole is known as Avogadro s constant (L) Avogadro s constant has a value of 6.023 x 10 23 mol -1. Example
More informationCHEMICAL EQUILIBRIUM (ICE METHOD)
CHEMICAL EQUILIBRIUM (ICE METHOD) Introduction Chemical equilibrium occurs when opposing reactions are proceeding at equal rates. The rate at which the products are formed from the reactants equals the
More informationCHEMICAL 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,
More informationSample Exercise 8.1 Magnitudes of Lattice Energies
Sample Exercise 8.1 Magnitudes of Lattice Energies Without consulting Table 8.2, arrange the following ionic compounds in order of increasing lattice energy: NaF, CsI, and CaO. Analyze: From the formulas
More informationStoichiometry. What is the atomic mass for carbon? For zinc?
Stoichiometry Atomic Mass (atomic weight) Atoms are so small, it is difficult to discuss how much they weigh in grams We use atomic mass units an atomic mass unit (AMU) is one twelfth the mass of the catbon-12
More informationCorrelation of Nelson Chemistry Alberta 20 30 to the Alberta Chemistry 20 30 Curriculum
Correlation of Nelson Chemistry Alberta 20 30 to the Alberta Chemistry 20 30 Curriculum Unit 5 Organic Chemistry General Outcomes Students will: 1. explore organic compounds as a common form of matter
More informationThermodynamics. Thermodynamics 1
Thermodynamics 1 Thermodynamics Some Important Topics First Law of Thermodynamics Internal Energy U ( or E) Enthalpy H Second Law of Thermodynamics Entropy S Third law of Thermodynamics Absolute Entropy
More informationChemical Reactions 2 The Chemical Equation
Chemical Reactions 2 The Chemical Equation INFORMATION Chemical equations are symbolic devices used to represent actual chemical reactions. The left side of the equation, called the reactants, is separated
More informationAP Chemistry 2009 Scoring Guidelines
AP Chemistry 2009 Scoring Guidelines The College Board The College Board is a not-for-profit membership association whose mission is to connect students to college success and opportunity. Founded in 1900,
More informationENTHALPY 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
More informationChapter 1: Moles and equations. Learning outcomes. you should be able to:
Chapter 1: Moles and equations 1 Learning outcomes you should be able to: define and use the terms: relative atomic mass, isotopic mass and formula mass based on the 12 C scale perform calculations, including
More information2. The percent yield is the maximum amount of product that can be produced from the given amount of limiting reactant.
UNIT 6 stoichiometry practice test True/False Indicate whether the statement is true or false. moles F 1. The mole ratio is a comparison of how many grams of one substance are required to participate in
More informationStates of Matter CHAPTER 10 REVIEW SECTION 1. Name Date Class. Answer the following questions in the space provided.
CHAPTER 10 REVIEW States of Matter SECTION 1 SHORT ANSWER Answer the following questions in the space provided. 1. Identify whether the descriptions below describe an ideal gas or a real gas. ideal gas
More informationMr. 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
More informationCoimisiún na Scrúduithe Stáit State Examinations Commission
2015. M33 Coimisiún na Scrúduithe Stáit State Examinations Commission LEAVING CERTIFICATE EXAMINATION, 2015 CHEMISTRY ORDINARY LEVEL TUESDAY, 16 JUNE AFTERNOON 2.00 TO 5.00 400 MARKS Answer eight questions
More informationUnit 9 Stoichiometry Notes (The Mole Continues)
Unit 9 Stoichiometry Notes (The Mole Continues) is a big word for a process that chemist s use to calculate amounts in reactions. It makes use of the coefficient ratio set up by balanced reaction equations
More informationChem 1100 Chapter Three Study Guide Answers Outline I. Molar Mass and Moles A. Calculations of Molar Masses
Chem 1100 Chapter Three Study Guide Answers Outline I. Molar Mass and Moles A. Calculations of Molar Masses B. Calculations of moles C. Calculations of number of atoms from moles/molar masses 1. Avagadro
More informationSTOICHIOMETRY OF COMBUSTION
STOICHIOMETRY OF COMBUSTION FUNDAMENTALS: moles and kilomoles Atomic unit mass: 1/12 126 C ~ 1.66 10-27 kg Atoms and molecules mass is defined in atomic unit mass: which is defined in relation to the 1/12
More informationChapter 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.
More information1. How many hydrogen atoms are in 1.00 g of hydrogen?
MOLES AND CALCULATIONS USING THE MOLE CONCEPT INTRODUCTORY TERMS A. What is an amu? 1.66 x 10-24 g B. We need a conversion to the macroscopic world. 1. How many hydrogen atoms are in 1.00 g of hydrogen?
More informationCoal-To-Gas & Coal-To-Liquids
Located in the Energy Center at Discovery Park, Purdue University Coal-To-Gas & Coal-To-Liquids CCTR Basic Facts File #3 Brian H. Bowen, Marty W. Irwin The Energy Center at Discovery Park Purdue University
More informationReturn to Lab Menu. Stoichiometry Exploring the Reaction between Baking Soda and Vinegar
Return to Lab Menu Stoichiometry Exploring the Reaction between Baking Soda and Vinegar Objectives -to observe and measure mass loss in a gas forming reaction -to calculate CO 2 loss and correlate to a
More informationChapter 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
More informationMEMORANDUM GRADE 11. PHYSICAL SCIENCES: CHEMISTRY Paper 2
MEMORANDUM GRADE 11 PHYSICAL SCIENCES: CHEMISTRY Paper 2 MARKS: 150 TIME: 3 hours Learning Outcomes and Assessment Standards LO1 LO2 LO3 AS 11.1.1: Plan and conduct a scientific investigation to collect
More informationHonors Chemistry: Unit 6 Test Stoichiometry PRACTICE TEST ANSWER KEY Page 1. A chemical equation. (C-4.4)
Honors Chemistry: Unit 6 Test Stoichiometry PRACTICE TEST ANSWER KEY Page 1 1. 2. 3. 4. 5. 6. Question What is a symbolic representation of a chemical reaction? What 3 things (values) is a mole of a chemical
More informationCHEMICAL REACTIONS AND REACTING MASSES AND VOLUMES
CHEMICAL REACTIONS AND REACTING MASSES AND VOLUMES The meaning of stoichiometric coefficients: 2 H 2 (g) + O 2 (g) 2 H 2 O(l) number of reacting particles 2 molecules of hydrogen react with 1 molecule
More informationCONSERVATION OF MASS During a chemical reaction, matter is neither created nor destroyed. - i. e. the number of atoms of each element remains constant
1 CHEMICAL REACTINS Example: Hydrogen + xygen Water H + H + + - Note there is not enough hydrogen to react with oxygen - It is necessary to balance equation. reactants products + H + H (balanced equation)
More informationMole Notes.notebook. October 29, 2014
1 2 How do chemists count atoms/formula units/molecules? How do we go from the atomic scale to the scale of everyday measurements (macroscopic scale)? The gateway is the mole! But before we get to the
More informationCHEM 120 Online: Chapter 6 Sample problems Date: 2. Which of the following compounds has the largest formula mass? A) H2O B) NH3 C) CO D) BeH2
CHEM 120 Online: Chapter 6 Sample problems Date: 1. To determine the formula mass of a compound you should A) add up the atomic masses of all the atoms present. B) add up the atomic masses of all the atoms
More informationUnit 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?
More informationChapter 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
More information7. 1.00 atm = 760 torr = 760 mm Hg = 101.325 kpa = 14.70 psi. = 0.446 atm. = 0.993 atm. = 107 kpa 760 torr 1 atm 760 mm Hg = 790.
CHATER 3. The atmosphere is a homogeneous mixture (a solution) of gases.. Solids and liquids have essentially fixed volumes and are not able to be compressed easily. have volumes that depend on their conditions,
More informationCP 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
More informationChapter 13 - Chemical Equilibrium
Chapter 1 - Chemical Equilibrium Intro A. Chemical Equilibrium 1. The state where the concentrations of all reactants and products remain constant with time. All reactions carried out in a closed vessel
More informationChapter 14. Review Skills
Chapter 14 The Process of Chemical Reactions ave you ever considered becoming a chemical engineer? The men and women in this profession develop industrial processes for the large-scale production of the
More information1. 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.
More informationCHEM 110: CHAPTER 3: STOICHIOMETRY: CALCULATIONS WITH CHEMICAL FORMULAS AND EQUATIONS
1 CHEM 110: CHAPTER 3: STOICHIOMETRY: CALCULATIONS WITH CHEMICAL FORMULAS AND EQUATIONS The Chemical Equation A chemical equation concisely shows the initial (reactants) and final (products) results of
More informationCHEM 101/105 Numbers and mass / Counting and weighing Lect-03
CHEM 101/105 Numbers and mass / Counting and weighing Lect-03 Interpretation of Elemental Chemical Symbols, Chemical Formulas, and Chemical Equations Interpretation of an element's chemical symbol depends
More informationSUGGESTION 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
More informationStoichiometry Exploring a Student-Friendly Method of Problem Solving
Stoichiometry Exploring a Student-Friendly Method of Problem Solving Stoichiometry comes in two forms: composition and reaction. If the relationship in question is between the quantities of each element
More informationPREPARATION 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
More informationMULTIPLE CHOICE QUESTIONS
MULTIPLE CHOICE QUESTIONS 1. Most components of energy conversion systems evolved very early; thus, the most fundamental aspects of energy metabolism tend to be: A. quite different among a diverse group
More informationSample 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.
More information