VIEWS: 7 PAGES: 54 POSTED ON: 1/6/2013
Thermochemistry Jeopardy xx This is the equation used to calculate the heat capacity of an object. What is C = c x m? This is the definition of specific heat capacity. What is the amount of energy required to change one gram of a substance by one degree Celsius? This is the substance on the specific heat capacities table that would require the most heat to increase its temperature by 10 oC. What is hydrogen? This is the definition of DH f o. What is the enthalpy change when one mole of a compound is formed from its elements? This is the definition of a closed system. What is a system that is closed to materials but not to energy? Changing the phase of a compound is a change in this type of energy. What is potential energy? A change between these two phases has the greatest change in enthalpy. What is liquid to gas. This type of curve shows the temperature and phase changes involved in changing a gas to a solid. What is a cooling curve? This is the number of steps that are involved in calculating the heat change in going from water vapour at 100 oC to ice at -5oC. What is 4 steps? This is the amount of heat required to convert 500 g of water at 10oC to water vapour. What is 1319 kJ? Calorimeters are useful for measuring enthalpy changes because they form this type of system. What is an isolated system? This is the heat given off when a food sample undergoes combustion in a bomb calorimeter (calibrated to 3.09 kJ/oC) and has a temperature change of 75 oC. What is 232 kJ of heat released by the sample? These are two situations when a calorimeter is not practical for measuring enthalpy change. What are non-aqueous solutions, reactions that form a significant amount of heat or reactions that are very slow? These three assumptions must be made when measuring enthalpy change using a calorimeter. What is the system is isolated, the heat exchange with the calorimeter are negligible and the properties of water remain the same? A 70.0 g sample of a piece of metal was heated to 95 oC and then placed in 100 g of water in a calorimeter. The water increasing in temperature from 20oC to 22oC. This is the specific heat capacity of the metal. What is 0.176 J/goC? A reaction with a negative enthalpy change is described as this. What exothermic? This law states that the enthalpy change of a process depends only on the initial and end conditions (pathway doesn’t matter). What is Hess`s Law? The change in enthalpy of these are defined as zero. What are elements in their standard states? Using these to determine enthalpy change is only an estimate. What are bond energies? To ensure a spontaneous reaction in going from a solid to a liquid, a reaction must have this sign for enthalpy. What is negative? Catalysts increase reaction rates by decreasing this. What is the activation energy? This is the slowest step in a reaction mechanism. What is the rate determining step? According to Le Chatelier’s Principle, these are the stresses that can cause a shift in equilibrium. What are temperature, concentration and pressure? An elementary step which involves a single molecule as a reactant is called this type of reaction. What is unimolecular? These are formed during the transition state of a reaction (part way between a reactant and product). What are activated complexes? Using bond energies, this is the estimated enthalpy change for the combustion of methane. What is -710 kJ?
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