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### 37 Cards in this Set

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 Definition: Thermochemistry The study of the relationships between chemistry and energy Definition: Energy The capacity to do work Definition: Work Force acting through a distance Definition: Heat The flow of energy caused by a temperature difference (high to low) Definition: Kinetic energy Energy associated with motion Definition: Thermal energy Energy associated with temperature (a type of kinetic energy) Definition: Potential energy Energy associated with position or composition Definition: Chemical energy Energy associated with the relative positions of electrons and nuclei in atoms and molecules (a type of potential energy) Definition: System The portion of the universe that is singled out for investigation Definition: Surroundings Everything outside of the system Units of energy joule (J) = 1kg m^2/s^2calorie (cal), the energy it takes to raise 1g of water 1°C = 4.184 JCalorie (C) = 1000 calkilowatt-hour (kWh) = 3.60 x 10^6 J Formula for change in energy of a reaction ΔE = Eproducts - EreactantsΔE is negative when the reaction gives off energyΔE is posative when the reaction absorbs energy Relationship between ΔEsys and ΔEsurr ΔEsys = -ΔEsurr Two factors that make up change in energy ΔE = heat transferred + work doneΔE = q + w Definition: Thermal equilibrium When heat transfer stops because the substances have reached the same temperature Definition: Heat capacity Symbol: CThe quantity of heat required to change the temperature of the system by 1°C Formula for heat capacity C = q/ΔT = J/°C also know the arrangement of that, q = C x ΔT Definition: Specific heat capacity Symbol: CsUnit: J/gThe intrinsic capacity of a substance to absorb heat. The amount of heat required to raise the temp. of 1g of the substance by 1°C Definition: Molar heat capacity Unit: J/mol x °C The amount of heat required to raise the temp. of 1 mol of a substance by 1°C Heat capacity is a _______ propertySpecific heat capacity and molar heat capacity are _______ properties extensive (depends on how much is being heated)intensive (a constant for that substance) Formula for heat using specific heat capacity heat = mass x specific heat capacity x temp. changeq = m x Cs x ΔT Relationship between qsys and qsurr qsys = -qsurr Formula for work w = -pressure x change in volumew = -P x ΔVconvert units from atm x L to J use the conversion factor 101.3 J = 1 atm x L Formula for change in heat of a reaction at constant volume ΔErxn = heat at constant volumeΔErxn = qv Definition: Calorimetry A process in which we deduce the thermal energy exchanged between a reaction and the surroundings by measuring the change in temp. of the surroundings Enthalpy means we are observing the system under constant _______ pressurei.e. how we feel about chem class Formula for enthalpy Symbol: HH = E + PV Formula for change in enthalpy ΔH = heat at constant pressureΔH = qp The difference between ΔE and ΔH ΔE represents change in heat and workΔH just represents change in heat Definition: Exothermic reaction A reaction that gives off heat to its surroundings Definition: Endothermic reaction A reaction that absorbs heat from its surroundings Standard states by state of matter Gas: pure gas at pressure of 1 atmLiquid or Solid: pure in its most stable form at 1 atm and the temp. of interest (usually 25°C)Substance in solution: at concentration of 1M Definition: Standard enthalpy change Symbol: ΔH°The change in enthalpy for a process when all reactants and products are in their standard states (that's what the ° means) Definition: Standard enthalpy of formation / standard heat of formation Symbol: ΔH°fFor a pure compound: The change in enthalpy when one mol of the compound forms from its constituent elements in their standard states.For a pure element in its standard state: ΔH°f = 0 Definition: Decomposition When a compound breaks down into it's constituent elements in their standard states. Reverse the sign on ΔH°f Rules for ΔHrxn in chemical equations 1. If the equation is multiplied by a factor, multiply ΔHrxn by the factor2. If the equation is reversed ΔHrxn changes sign3. If an equation is the sum of a series of steps the the ΔHrxn for the overall rxn is the sum of the ΔHrxn's for each step To calculate the ΔH°frxn Subtract the enthalpies of formation of the reactants multiplied by their stoichiometric coefficients from the enthalpies of formation of the products multiplied by their stoichiometric coefficients.ΔH°frxn = ∑npH°f(products) - ∑nrH°f(reactants)