Energetics Flashcards
what are exothermic reactions
Exothermic reactions = reactions that release energy to the surroundings
what are endothermic reaction
Endothermic reactions= reactions that absorb energy from the surroundings
what are the latin for endo exo and thermic
Thermic = heat
Exo = out
Endo = in
what are some examples of exothermic reactions (4)
Examples of exothermic reactions:
BURNING - combustion reactions - in combustion something reacts with oxygen
2. Metals reacting with acid
3. Neutralisation reactions
4. displacement reactions -
5. Calcium Oxide and Water - it releases so much heat that it causes the water to boil and become steam. Calcium hydroxide (slaked lime) is produced
what is formula for calcium oxide called
CaO = quicklime
what is the formula for calcium hydroxide
Ca(OH)2 =slaked lime
how do you slake quicklime
adding water = slaking it
what is the displacement reaction between aluminium and iron (III) oxide
2Al + Fe2O3 —> 2Fe + Al2O3
what is enthalpy change
In a reaction, you can measure the enthalpy change, which is the amount of heat energy that is absorbed or released in a reaction
what is the symbol for enthalpy change
The symbol for enthalpy change is Delta (triangle) H –> the delta means change
can you have enthalpy on its own
You cannot have enthalpy on its own, you can only have enthalpy change
what is the uni for enthalpy change
The unit for enthalpy change is kJ/mol - think of it as the amount of energy change per mol of reactant
describe the energy change diagrams for endothermic
check starred msgs
describe the energy change diagrams for exothermic
check starred msgs
what is BENDOMEX
BENDOMEX
Breaking is ENDO, Making is EXO
how dooes bonds relate to the energy absorbed/released in a reaction
in a reaction, the bonds between atoms are broken down, and then new bonds are made to create new compounds
When breaking bonds, energy is required, so energy is absorbed INTO the reaction, so you see the energy in the reaction profile increase
When making the bonds, energy is released OUT of the reaction, so you see the energy of the reaction go down.
what is and whats an exmaple of endothermic reaction
An endothermic reaction is one where the heat energy is absorbed from the environment
An example of endothermic reaction is thermal decomposition (breaking a compound down using heat)
copper carbonate –> copper oxide + carbon dioxid
what is a common source of error in enthalpy change expirements
The largest source of error in this experiment is the large amounts of heat loss to the surroundings
what are some common sources of heatloss in an enthalpy change experiment
Sources of heat loss:
Warm water gives out some heat to the air
The open flame of the spirit burner transfers some heat to the air surrounding it as opposed to heating the water
Heat is also used to increase the temeprature of the copper can and the thermometer instead of the water
why does unintended heatloss hinder an enthalpy change experiment
These factors can result in an incorrect value of enthalpy change obtained from the reading
why is incomplete combustion a problem for enthalpy change experiements (2)
We are using the mass of ethanol as a factor for how much energy is being used
In this assumption, we rely on the fact it is ALWAYS releasing energy via complete combustion
HOWEVER, if there is insufficient oxygen, incomplete combustion would take place, which is a problem as incomplete combustion releases less energy than complete
what is specific heat capacity
Specific heat capacity - the amount of energy, needed for 1g of a substance to get hotter by 1degrees celsius
what is the equation for enthalpy change
Q = m x c x (delta)T
what is Q in the enthalpy change equatiom
enthalpy change
