| Question | Answer |
| How do you calculate enthalpy change | Subtracting the enthalpies of formation of the reactants from the enthalpies of formation of the products. Multiply the enthalpies of formation by integers as required by the balanced equation. When reaction reversed, sign changes ∆H. Elements in their standard states are not included |
| standard state | Depend on concentrations of substances involved. Can measure on the changes in property. For a compound: Gas = 1atm, Pure substance in condensed state is the pure liquid or solid, Substance in solution = 1mol. For an element, 1 atm and 25 ˚C |
| Degree symbol on a thermodynamic function | Corresponding process has been carried out under standard conditions |
| Standard Enthalpy of Formation ∆Hf˚ | Change in enthalpy that accompanies the formation of one mole of a compound from its elements with all substances in their standard states |
| How do you solve a Hess's Law problem | Several reactions to be manipulated and combined to finally give the reaction of interest. Work backward from the required reaction. Reverse any reactions as needed to give either required reactants and products. Multiply reactions to give the correct numbers of reactants and products |
| What does the sign of ∆H indicate? | Direction of heat flow at constant pressure. |
| 2 characteristics of ∆H for a reaction | If a reaction is reversed, the sign of ∆H is also reversed. The magnitude of ∆H is directly proportional to the quantities of reactants and products in a reaction. If the coefficients in a balanced reaction are multiplied by an integer, the value of ∆H is multiplied by the same integer |
| hess's law | Change in enthalpy in going from some initial state to some final state is independent of the pathway. In going from a particular set of reactants to a particular set of products, the change in enthalpy is the same whether the reaction takes place in one step or in a series of steps. ∆H = enthalpy change |
| constant volume | No work is done. Energy change determined by measuring increase in the temperature of water and other calorimeter parts. ∆E = q +w = qv |
| energy (as heat) released by reaction | =c x m x ∆T |
| constant pressure calorimetry | Measurement of heat using a simple calorimeter. Keep pressure constant. ∆H = qp |
| molar heat capacity | Heat capacity per mole |
| specific heat capacity | heat capacity per gram |
| heat capacity | C = heat absorbed / increase in temperature |
| calorimetry | Science of measuring heat based on observing temperature change |
| calorimeter | Device used experimentally t determine the heat associated with a chemical reaction |
| ∆H = | H products - H reactants. Endothermic: ∆H = +. Exothermic: ∆H = - |
| enthalpy | H = E + PV. State function. At constant pressure, (where only PV work is allowed), the change in enthalpy ∆H of the system is equal to the energy flow as heat. Heat of reaction = change in enthalpy |
| w = -P∆V | Work done to an expanding gas |
| two parts of thermodynamic quantities | Number: Magnitude of change. Sign: Reflects system's point of view, + = endothermic, - = exothermic |
| internal energy | E. Sum of kinetic and potential energies. ∆E = q + w |
| first law of thermodynamics | The energy of the universe is constant. Same as law of conservation of energy |
| thermodynamics | Study of energy and its interconversions |
| exothermic | Energy flows out of a system. Some of the potential energy stored in the chemical bonds is being converted to thermal energy via heat. ∆(PE) transferred to surroundings through heat |
| state function/property | A change in function in going from one state to another state is independent of particular pathway taken between two states. Eg. Total energy. Work and heat are not state functions |
| work | force acting over a distance, can transfer through either heat or work |
| heat | Transfer of energy between two objects due to a temperature difference. Not a substance contained by an object |
| temperature | Property that reflects the random motions of the particles in a particular substance |
| frictional heating | Kinetic energy transferred to a surface as heat |
| kinetic energy | energy due to motion of the object. Depends on the mass of the object m and velocity v. KE = 1/2 mv^2 |
| potential energy | energy due to position or composition |
| law of conservation of energy | Energy can be converted from one form to another but can be neither created nor destroyed |
| energy | Capacity to do work or to produce heat |
33 cards - created feb 20, 5:14pm