Topic 5: Energetics Flashcards
Exothermic reaction
heat is given away to the rest of the universe creating more thermodynamicly stable products than reactants.
Energy
Ability to do work (heat)
System
the area of interest, the place where the chemical reaction occurs.
Open system
can exchange matter and energy with the rest of the universe
Closed system
can exchange energy with the rest of the universe but not matter.
Enthalpy
“the heat inside” - the reservoir of energy in a compound
Endothermic
heat is used by the system and have to be added from the suroundings
Common exothermic reaction; Combustion reactions
When a compound is bured in excessor oxygen CO2 and water as products
Common exothermic reaction; Neutralization reactions
e.g. when HCL reacts with NaOH or be precise. Energy Always negative
Common endothermic reaction; Photosynthesis
6CO2 (g) + 6H2O -> C6H12C6 (aq) + 6O2 (g)
Energy always positive, because it is needed for the reaction to take place.
What does the increase in temperature depend on?
- the mass of the object
- the heat added
- the nature of the substance
What is the formula for heat change.
Heat change = mass x specific heat capacity x temperature change
When does endothermic reactions occurs?
When there is an increase in disorder of the system.
What is enthalpy change of combustion?
The heat produced when one mole of a substance is burned in excess oxygen
The standard enthalpy of formation of a substance?
The enthalpy change that occurs when one mole of the substance is formed from its elements in their standard states under standard conditions
