Chemical Energy Flashcards
What is the change in energy in a chemical reaction known as ?
the enthalpy change
What does a highly exothermic reaction require ?
cooling as a lot of heat energy will be released
What does a highly endothermic reaction require?
infrastructure to supply heat to maintain the reaction
What is the experimental set up for calculating the energy released by a fuel such as an alcohol?
tripod burning fuel water copper cup thermometer
What calculation can be used to calculate the energy transferred to the water when measuring the energy released by a fuel?
E= cm^t ^ = delta
What must the mass of water be in?
KILOGRAMS (1kg = 1000g)
What is the enthalpy of the combustion of substance?
the heat energy released when 1 mole of a substance burns completely in oxygen
What must you remember about the enthalpy change for an exothermic reaction?
it is negative and heat energy is released to surroundings
What is the equation used to find the temperature increase?
^T=Eh/cm
Why might the theoretical enthalpy of combustion be greater than the experimental value?(3)
heat loss to surroundings
incomplete combustion of (ethanol)
loss of (ethanol) through evaporation
What does Hess’ law state?
the enthalpy of a reaction is independent on the chemical route taken
What is the equation according to Hess’law following the formation of carbon dioxide?
^H= ^H1+^H2
To understand Hess’ law, what enthalpy equations must be considered?
enthalpy of combustion
enthalpy of formation
What must you remember about enthalpy of formation?
only 1 mole of a substance is being produced from its elements
What can bond enthalpies be used to estimate?
the enthalpy change occuring for a gas phase reaction by calculating the energy required to break bonds in reactants and the energy released when new bonds are formed in the products
