Energetics Flashcards
Explain an Endothermic Reaction (3)
Reactions that absorb more energy from the surroundings when breaking bonds then release when making bonds
Positive Enthalpy Change
Products have Higher Enthalpy then Reactants
Explain an Exothermic Reaction (3)
Reactions that release energy to the surroundings
Negative Enthalpy Change
Products have Lower Enthalpy then Reactants
What type of reaction is Breaking Bonds?
What Type of Reaction is making bonds
What is the Equation for Enthalpy Change (bonds)
Enthalpy Change = Total Energy to break bonds - Total energy released forming bonds
Define Hess’ Law
Heat energy lost =
mass of water or solution x specific heat capacity x temperature change
How do you work out Enthalpy change via Calormetry
1) change q from J to KJ
2) Divide by moles of fuel used
In enthalpy of formation hess cycle the arrows go (year 12)
Elements in their standard states —-> Compounds
Down to Up
In enthalpy of combustion hess cycle (year 12) the arrows go from
Compounds—-> Compounds (when burnt in oxygen)
Up to Down
Explain how varing pressure/temperature to increase yield might affect the profit of an organisation
- (Increasing ) Maintaining a high pressure/ high temperature environment is expensive, High operating costs, equipment costs and maintenance fees
-(Decreasing) Reaction may have a higher yield but rate of reaction may be too slow, decreasing the rate of production.
