CHEM 1061 1st Edition Exam 2 Study Guide Lectures 11 20 Lecture 11 February 13 What is Avogadro s Law Volume is proportional to amount In mol Pressure and Temperature are constants What is STP STP is standard temperature and pressure When gas is calculated at STP it is calculated at 0 degree Celsius and 1 atm How can you calculate density using PV nRT Using the PV nRT equation you can substitute mass molar mass for n and rearrange the equation The rearranged equation would be molar mass P RT mass V density Lecture 12 February 16 How can you calculate molar mass of a gas using PV nRT N is mol therefore you can rewrite the equation to look like PV mass molar mass RT and solve for molar mass while filling in appropriate known values What is the mole fraction A mole fraction is the number of moles of a specific gas over the total number of moles What is an important thing to consider when calculating gases over water When calculating gases over water you need to take into consideration the vapor pressure of water You do not need to memorize these values but they are found on table 5 2 of your textbook Lecture 13 February 18 What is the difference between potential and kinetic energy Potential energy is the energy due to the position of the object Kinetic energy is the energy due to the motion of an object An object must be moving to have kinetic energy Is E positive or negative when energy is released into its surroundings When E is released to its surroundings the reaction is exothermic and has a negative value As opposed to that when E absorbs energy it has a positive value and is endothermic E q w What does this mean This is an equation for change in energy Q stands for heat and w stands for work If there is ONLY heat than work is always 0 If there is ONLY work than heat is always 0 If both are present you must look at the magnitude of to determine the value of E Lecture 14 February 20 What is Enthalpy What is the variable it is represented by Enthalpy is the heat absorbed or released at a constant pressure It is represented by an H What is an endothermic reaction An endothermic reaction is one that absorbs or needs energy to complete the reaction and has a positive value of change in enthalpy How do you calculate Specific Heat Capacity c Specific Heat Capacity is the quantity of heat required to change the temperature of 1 g of an object by 1 Kelvin To calculate Specific Heat Capacity use the equation c q mass x T The units for specific heat capacity is J g x K Lecture 15 February 23 What is an important aspect to consider when calculating heat lost to both water and a calorimeter When heat is lost to both water and a calorimeter you have to consider the calorimeter There is no mass component in calculating the heat lost to the calorimeter because you cannot have half of a calorimeter or one third or five eighths Since q gain q lost and q lost is now to BOTH the water and the calorimeter the q gain q H2O q cal Q cal c cal x change in temperature How is the change in enthalpy effected if the reaction is reversed If the reaction is reversed for example if liquid water froze into solid water and the reaction was reversed and the ice was melted the change in enthalpy would switch signs Enthalpy change is proportional to the equation If you flip the equation the positive negative sign also changes What is the enthalpy when 2 63g P s reacts with excess Br2 l 2 63 g P s x 1 mol P s 30 97 g P s x 243 kJ 2 mol P s 10 3 kJ Lecture 16 February 25 Find the Change in Enthalpy for NH3 g HCL g NH4Cl s Given 1 N2 g 3 2H2 g NH3 g H 45 9kJ 2 H2 g Cl g HCl g H 92 3kJ 3 N2 g 2H2 g Cl2 g NH4Cl H 314 4kJ Flip 1 so NH3 is a reactant also flip H sign NH3 g 1 2N2 g 3 2 H2 g H 45 9 Flip 2 so HCl is a reactant also flip H sign HCl g 1 2H2 g Cl2 g 92 3kJ MAKE SURE EQUATIONS MATCH Reactants NH3 g HCl g 1 2N2 g 2H2 g Cl g Products N2 g 3 2H2 g H2 g 1 2Cl2 g NH4Cl s THEY MATCH Add up 1 3 so they balance cancel out to the target Do the same manipulations to H H overall H1 H2 H3 45 9kJ 92 3 kJ 314 4 kJ 176 2 kJ Lecture 17 February 27 What kind of reactions can you find how much energy there is per mole of fuel reacted Heat of combustion is the type of reaction which tells you the energy per mol fuel reacted Find the change in enthalpy of the equation NH3 g HCL g NH4Cl s H 1 2 N2 g 3 2H2 g NH3 g H f 45 9kJ mol H2 g Cl2 g HCl g H f 92 3kJ mol N2 g 2H2 g 1 2Cl2 g NH4Cl s H f 314 4 kJ mol H rxn mx H f products n x H f reactants H rxn 1mol NH4Cl H f NH4Cl 1mol NH3 H f NH3 1mol HCl H fHCl H rxn 1mol 314 4kJ mol 1mol 45 9kJ mol 1mol 92 3kJ mol H rxn 176 2 kJ Use H f values to calculate H rxn for 4Al s 3MnO2 s 2Al2O3 s 3Mn s H f kJ mol Al 0 MnO2 520 9 Al2O3 1676 Mn 0 2mol 1676 3mol 520 9 1789 3 kJ What is Quantum Mechanics The theory that explains the fundamental nature of energy and matter and accounts for atomic structure Lecture 18 March 2 Calculate the Frequency of LiCl emission at 680 nm 3 00 x 10 8 m s 680 nm x V 3 00 x 10 8 m s 6 8 x 10 7 m x V 3 00 x 10 8 m s 6 80 x 10 7 m 4 41 x 10 14 Hz What is a quantum A quantum is a fixed amount Calculate the energy associated with Violet and Red light Violet Light 400 nm Red Light 700nm E hc Violet E 6 626 x 10 34 Js 3 00 x 10 8 m s 4 00 x 10 7m 4 97 x 10 19 J Red E 6 626 x 10 34 Js 3 00 x 10 8 m s 7 00 x 10 7 m 2 84 x 10 19 J Lecture 19 March 4 When the change in E is negative the atom absorb or emit energy When E is negative the atom emits energy Also known as when N final N initial Calculate E for transition movement …