Energy & Chemical Change Flashcards
(25 cards)
What is enthalpy
Measurement of energy in a thermodynamic system
What is the formula for ∆H
Hf(enthalpy of products) - Hi(enthalpy of reactants)
What is an Endothermic reaction
Reaction in which heat is absorbed by system
What is an Exothermic reaction
Reaction in which heat is released in a system
Why do we measure the change in heat energy instead of the total amount of energy available in a system
It’s close to impossible to find the exact amount of heat present in a system
What is the relationship between reactants and products of an Endothermic reaction
The products have higher energy than the reactants
Why is the ∆H of an Endothermic reaction positive
Products have higher energy than the reactants
What is the relationship between reactants and products of an Exothermic reaction
The energy of the products is lower than the energy of the reactants
Why is ∆H of an Exothermic reaction negative
Products have less energy than reactants
What type of reaction is Condensation
Exothermic
What type of reaction is melting
Endothermic
What type of reaction is evaporation
Endothermic
What type of reaction is Combustion
Exothermic
Define thermodynamics
Science of relationship between heat, work, temperature and energy
What type of reaction occurs when bonds are formed. Why?
Exothermic [when bonds are formed energy is released]
What type of reaction occurs when bonds are broken. Why?
Exothermic [to break a bond, heat energy must be added]
Name one poisonous gas produced by combustion
Carbon monoxide
What is activation energy
Minimum amount of energy required for compound to result in chemical reaction
What is activated complex
Stage where bonds in reactants are breaking while new ones are forming to create new products
What is the formula for activation energy [Ea]
Ea =Activated complex - E.reactants
When you sketch an Endothermic energy diagram at which two points does Activation energy lie in-between
It lies in between reactants and activated complex or between reactants and catalysts (if given)
On an Endothermic energy diagram at which two points does ∆H lie in between
Reactants and products
What is a catalyst
Chemical substance that lowers activation energy required without taking part in the reaction
How do you measure energy released in an energy diagram
Energy released = Activated complex - products
