Chemistry, 6: Energy changes in chemical reactions

Cards (13)

Exothermic reactions is where energy is transferred to the surrounding
What are examples of exothermic reactions?
Combust
Respiration
Neutralisation
Endothermic reactions is when energy is absorbed from the surroundings
What are examples of endothermic reactions? 
Photosynthesis
Thermal decomposition
When magnesium ribbon is added to dilute HCl, the temperature of acid increases
It is an exothermic reaction
When sodium hydrogen-carbonate is added to HCl, the temperature of the acid decreases
This was endothermic
In an exothermic reaction, the energy contents of reactants is greater than the energy contents of the products
Energy is being lost to the surroundings
Enthalpy change is negative
In an endothermic reaction, energy contents of reactants is less than energy contents of products
Energy is being absorbed from the surroundings
Enthalpy change is positive
The activation energy is the minimum amount of energy required for reaction to occur
In an exothermic reaction, energy released on forming new bonds is greater than energy needed to break old bonds.
In an endothermic reaction, energy needed to break old bonds is greater than energy released when new bonds are formed, energy change is small.
In endothermic reactions, energy is transferred from the surroundings to the reactants to break bonds.
In exothermic reactions, energy is released from the bonds between the reactants and transferred to surroundings as new bonds form.