Reactions that absorb heat are called __________________ * Assignment #1 Determine if the following processes are endothermic or exothermic? Then Explain why. When solid potassium bromide (endo or exo) is dissolved in water (endo or exo), the solution gets colder. Natural gas ( CH4 ) is burned (endo or exo) in a furnace to heat the house (endo or exo). When concentrated H2SO4 (endo or exo) is added to water (endo or exo), the solution gets very hot. Water (endo or exo) is boiled in a teakettle while sitting on the stove “element” (endo or exo). Podcast 4.3: Enthalpy Enthalpy is a State Function The value for a state function depends only on Enthalpy, H, is also a state function ___________________ Function accounts for H = ΔH = for a gas => work = ΔE = SO… ΔH = Change in enthalpy = Enthalpies of Rxn ΔH = So… ΔH = this can also be called the heat of reaction or ΔHrxn IF… ΔH is - => __________________________ ΔH is + => __________________________ Thermochemical Equations a chemical reaction that shows Example Calculations with Enthalpy
Example 1: Calculate the Enthalpy change for the combustion of CH4 to form CO2 and liquid water. CH4 (g) + 2O2 (g) → CO2(g) + 2H2O (g) ΔH = 2H2O (g) → 2H2O (l) ΔH = -88 kJ CH4 (g) + 2O2 (g) → CO2 (g) + 2H2O (l) ΔH = ? Example 2: The enthalpy of combustion of to CO2 is -393.5 kJ/mol and the enthalpy of combustion of CO to CO2 is -283.0 kJ/mol. C (s) + O2 (g) → CO2 (g) ΔH = -393.5 kJ CO (g) + ½ O2 (g) → CO2 (g) ΔH = -283.0 kJ Using this data, calculate the enthalpy of combustion of C to CO by the reaction C(s) + ½ O2 (g) → CO(g) Assignment #6 Calculations of Enthalpy from Related Reactions 1. Calculate the enthalpy for the following reaction: 2. Calculate the enthalpy for the following reaction: 3. From the following enthalpy changes, calculate the value of ∆H for the reaction of C + O2 CO2 4. From the following enthalpy changes, calculate the of ∆H for the reaction of PCl3 + Cl2 PCl5 5. From the following enthalpy changes, calculate the value of ∆H for the reaction of C2H5OH CH3OCH3
A concentrated solution of ammonia is added to a solution of zinc iodide. Hydrogen sulfide gas is bubbled into a solution of mercury(II) chloride. Solid calcium hydride is added to distilled water. Solid aluminum oxide is added to a solution of sodium hydroxide. Solid calcium oxide is heated in the presence of sulfur trioxide gas. Equal volumes of 0.1-molar sulfuric acid and 0.1-molar potassium hydroxide are mixed. Calcium metal is heated strongly in nitrogen gas. A concentrated solution of hydrochloric acid is added to powdered manganese dioxide and gently heated. A bar of zinc metal is immersed in a solution of copper(II) sulfate. A solution of copper(II) sulfate is added to a solution of barium hydroxide. An excess of sodium hydroxide solution is added to a solution of magnesium nitrate. Solid lithium hydride is added to water. Solutions of ammonia and hydrofluoric acid are mixed. A piece of aluminum metal is added to a solution of silver nitrate. An excess of nitric acid solution is added to a solution of tetraaminecopper(II) sulfate. Carbon dioxide gas is bubbled through water containing a suspension of calcium carbonate. Thermodynamics: The study of energy relationships (Chapter 19) Podcast 14.1 Spontaneity Spontaneous Reactions the formation of ________ *Does NOT: *_______________ and _______________ have impacts on spontaneous reactions