Gen Chem 2 complete study guide All the notes were taken from the book PowerPoint lecture so all areas are covered Nature of Energy Heat is the ow of energy caused by differences in temperatures Energy is anything that has the capability to do work work is a force acting over a distance Energy is a quantity an object possess Heat or work are ways of exchanging energy with other objects Kinetic energy is energy of motion or energy that is being transferred Thermal energy is energy associated with temperature form of kinetic energy molecular vibration Potential energy is energy stored in an object or associated with the position or composition of an object energy cannot be created nor destroyed when energy is transferred from one object to another it can be converted but the same total energy remains the same System materials we are studying the energy changes within Surroundings anything the system can exchange energy with KE 1 2mv 2 1 Joule energy needed to move 1KG 1m s 1 cal energy needed to raise one gram of water 1 degree Celsius Pg 238 table System gains energy System releases heat energy E q w q m heat Thermodynamics the study of energy and it s inter conversions The sum of energy changes must be zero Universe energy 0 system energy surrounding energy The rst law of thermodynamics is conservation of energy Therefor you can never design a system that will continue to produce energy without some source of energy Internal energy is the sum of all the kinetic and Potential energy in the particles system State functions do not distinguish the differences in energy just nal Energy diagrams are a graphical way of showing direction of energy ow Heat exchange Exchange of thermal energy between the system an the surroundings Temperature is the measure of thermal energy in a sample of matter Heat ows from matter with a high temperature to matter of a low temperature until both objects reach the same temperature Thermal equilibrium q hot q cold Heat capacity Units of C are J C or J K q C change in T Increase in temperature is directly proportional to the heat absorbed The proportionality constant is the heat capacity C The larger the heat capacity of an object being studied the smaller the temperature rise for a given amount of heat Speci c heat capacity is the amount if heat required to raise one gram of a substance one degree Celsius Molar heat capacity is the amount if heat required to raise one mole of a substance one degree Celsius The heat capacity of an object depends on the matter in mass Dependent on the type of material q mass x speci c heat x temperature change Example 6 2 How much heat is absorbed by a copper penny with mass 3 10 g whose temperature rises from 8 0 C to 37 0 C Practice Calculate the amount of heat released when 7 40 g of water cools from 49 to 29 C water s speci c heat is 4 18 J g C PV work is cause by a volume change against an external pressure When gas expands is change in volume is positive but the system iI doing work so it energy is negative work gas external pressure x change in volume Example 6 4 If a balloon is in ated from 0 100 L to 1 85 L against an external pressure of 1 00 atm how much work is done 101 3 J 1 atm L If volume is constant w 0 w P change in V 0 Change in energy of the system heat of system E q w Enthalpy is the sum of internal energy and product of pressure and volume H E PV The change in enthalpy is the heat evolved Enthalpy and energy are similar unless large amounts of gasses are reacted Delta H is negative heat is released exothermic Delta H is positive heat is absorbed endothermic Example 6 5 When 1 010 g of sugar is burned in a bomb calorimeter the temperature rises from 24 92 C to 28 33 C If Ccal 4 90 kJ C nd E for burning 1 mole Example 6 7 How much heat is evolved in the complete combustion of 13 2 kg of C3H8 g 2044 kJ mol Endothermic reactions Exothermic reactions Thermal energy from the conversion of reactants to products are released increasing the surrounding temperature The chemical Potential energy is converted to kinetic energy and released as heat Old bonds are broken and new bonds with less chemical Potential energy are formed The surroundings temperature drops because absorption of thermal energy by the reaction old bonds are broken and new bonds with a higher Potential energy are formed To acquire this extra energy thermal energy of the surroundings are absorbed Standard states State of materials at a de ned set of conditions The standard enthalpy change is when all their reactants and products are in their standard stage Standard enthalpy of formation is for a reaction forming one mole of a pure substance Pure gas at 1 atm Solids at 25 degrees Formation reactions Reactions of elements in their standard states to form 1 mole of a pure substance Standard enthalpy of change Any reaction can be rewritten as the sum of formation reactants Enthalpy of reaction sum of products enthalpy sum of reactants enthalpy Called Hess Law Hess Law Given the following information 2 NO g O2 g 2 NO2 g H 116 kJ 2 N2 g 5 O2 g 2 H2O l 4 HNO3 aq H 256 kJ N2 g O2 g 2 NO g H 183 kJ Calculate the H for the reaction below 3 NO2 g H2O l 2 HNO3 aq NO g H Chemical Kinetics is the study of the factors that effect reaction rates in chemical reactions Such as temperature Concentration Pressure The rate of a reaction is a measure of how fast the reaction makes products The ability to control the rate of reaction is important Speed change in distance change in time Rate change in concentration change in time Rate change in product time change in reactants time For chemical reactions As time goes on for chemical reactions their rate slows down For stoichiometry reaction rates Concentration of reactants decrease Equilibrium is reached Change the coef cient substances to 1 coef cient Average rates slope of graph Instantaneous rates derivative of point Continuous monitoring Polarimetry measuring the change in the degree of rotation of plane polarized light caused by a component over time Spectrophotometry measuring the amount of light of a particular wavelength absorbed by one component over time Total pressure the total gas pressure mixed is stoichiometrically related to the partial pressures Speci c times during the reaction take aliquots to take qualitative analysis Titration Gravimetric Gas chromatography can measure the components of a gas mixture Factors effecting reaction rate Nature of reactants size or physical state Temperature Catalysis