Unit 3 Chemical Energy Flashcards
What id enthalpy?
The chemical energy involved in a chemical reaction
What is enthalpy change?
Is the difference in energy between the reactants and the products
What equation is used to calculate enthalpy change?
Eh=c m triangleT
C specific heat capacity of water
M mass of water(kg)
Triangle T change in temp
Why is enthalpy change a important consideration in chemical industry?
Endothermic reactions
May generate additional costs as heating is necessary to maintain the rate
Exthoermic reactions
Generate enough heat that no additional heating is needed
What is the enthalpy of combustion?
Of a substance is the enthalpy change(energy released) when one mole of substance burns completely in oxygen
What are these reactions always?
As the substance is burned heat energy is realsied making the reaction exthothermic so the process always has a negative value
How do u set up a experiment to measure energy realesd by a fuel when burned?
A sprint burner,metal breaker,water themometer
What measurments need to be taken when determining energy realesd when a fuel burns?
The start and final temp of water which allows temp change calculation
The mass of burner before/after the experiment allows to calculate mass of alcohol burned
Give a reason why your experimental enthalpy value differs from textbook value?
Heat loss to surrounding
Incomplete combustion
What does hees law state about enthalpy change?
States that. The enthalpy change for a chemical reaction is independent of the route taken
What is bond enthlpy?
The energy required to break a covelent bond between two atoms
Is energy required or released when bonds are broken, endothermic or exothermic?
Energy is required
Endothermic
Is energy required or released when bonds are made, endothermic or exothermic?
Energy is released
Exothermic
What do the bond enthlpys in the databook mean?
Are the energies required to break one mole of a particular bond between a pair of atoms in the gaseous state
