M2 - Chem thermodynamics Flashcards
What is Energy?
The capacity to do work or transfer heat
What is work?
E used to change position
What is heat
E used to change temp
Where is the potential E in chem
In the charged atoms
*Chem bonds store electrostatic potential energy
What is a chemical bond?
Interaction between nuclei and e-s
What changes electrostatic PE?
Where nuclei and e-s are and this can be changed to other forms of E
1st law of thermodynamics
Energy cannot be created or destroyed, it can only be transferred and transformed from one type to another
Why is change in heat used?
Because PE of the reactants is harder to measure
What is an exothermic reaction?
When reactants have higher E, bonds broken to form products with less E and heat, energy given out ∆H = -ve (as products lost E)
What is an endothermic reaction?
When reactants have lower E, bonds formed to form products with high E and heat, energy absorbed to form bonds and store the E in bonds ∆H = +ve (as products have E)
What is Enthalpy?
Heat Energy at constant pressure eg Atmospheric pressure
Why is H used mostly?
Because most chem reactions in the body are under the influence of atmospheric pressure, which is constant
∆rq =
∆rH = H(products) - H(reactants)
Why is Enthalpy a state function?
Because Enthalpy stays the same regardless of the path it takes
What is a formation enthalpy?
Where ONLY one mole of the product is formed from its constituent elements at standard states
