CHM 104 1st Edition Exam 3 Study Guide Lecture 1 March 23 Introduction to Complex Ions What are complex ions and how are they formed How is the K constant affected Kf the K constant of formation formation being the production of a product solid When a transition metal reacts with a ligand or a compound with pairs of lone electrons it forms into a complex ion Cu2 4CN Cu CN 42 CN has two pairs of unshared electrons Cu2 is a transition metal The overall charge on the product is 2 because 2 from the copper subtracted by 4 1 charges 2 4 2 The Kf the reaction is more favorable A complex ion is more stable because it has lower energy Complex ion equations are extremely product favored How can these equations be made written Consider the following equation AgCl s Ag Cl Ksp 1 6 10 10 This small K constant means that there is a SMALL amount of Cl in the solution To change this some Ag can be removed and placed with something to make a complex ion Ag 2NH3 Ag NH3 2 Kf 1 7 107 Now these two equations can be added together and will make an equation with more Cl in the final solution AgCl s Ag Cl Ag 2NH3 Ag NH3 2 AgCl s 2NH3 Ag NH3 2 Cl Introduction to Thermochemistry and Thermodynamics What is thermochemistry How does heat transfer through a system and its surroundings Kinetic energy also known as KE 1 2 mv 2 is THERMAL ENERGY Thermal Energy the energy of MOTION of molecules ions and atoms Potential Energy Stored form of energy due to position 1st Law of Thermodynamics Total amount of energy is constant can t be created or destroyed just changes forms If one side of an equation contains more potential chemical energy then the other side has more thermal energy March 25 Lecture Introduction to Systems Surroundings and Energy Transfer System A specific finite part of the universe that is being studied Surroundings Everything else around the system Energy Transfer Work Force Distance o If a gas is squished into a smaller volume surroundings do work on the system with more energy Heat q to transfer thermal energy Only goes in one direction Heat absorbed from environment surroundings q positive Heat released to surroundings from system q negative State Functions Independent of sample history independent of path of heat transfer The end change of heat is the only thing that matters Only thing that matters is that heat goes from point A to point B March 27 Lecture Consider the following equation 2H2O H2 O2 When 15 grams of H2 is burned in O2 how much heat in kJ is released Equation H2 O2 H2O H 241 8 kJ Step 1 Find the number of moles of hydrogen 1 mol 2 0 grams H2 15 grams 7 5 mol H2 Step 2 Convert to kJoules 7 5 mol H2 241 8kJ 1mol H2 from equation 1 8 103 kJ H Calorimeter Measuring heat transfer Specific Heat s Quantity of heat required to raise the temperature of exactly 1 gram of a substance by 1 degree celcius q mass S T Heat Capacity C quantity of heat needed to raise T of a certain object up by 1 degrees Celsius units are J degrees Celsius Qreaction q water q calorimeter Hess Law For a multi step process Hreaction Sum of H of all steps H reaction Sum of Hf products Sum of Hf reactants April 3 Lecture When Does a Reaction Occur Depends on Conditions like temperature pressure catalyst kinetics Thermodynamics will react when nature wants it to When spontaneous Most spontaneous process Decrease energy of system Randomness is favored over order A solid has less disorder more order and less ENTROPY More random motion higher entropy S Something that has a low chance of happening can be ignored of happening at all Similar to which reactions are actually possible