1B2 Thermodynamics Flashcards
What is exothermic?
Heat energy is given out so the temperature of the surroundings increases
Minus symbol
What is endothermic?
Heat energy is taken in so the temperature of the surroundings decreases
Positive symbol
Define enthalpy change?
The amount of heat energy taken in or given out during any change in a system at constant pressure
Define standard enthalpy change?
The enthalpy change for a reaction at 298 K and 100 kPa with all reactants and products in their standard states
What is specific heat?
A substance is the heat required to raise the temperature of 1 gram of a substance by 1 Kelvin. It is measured in J g–1 K–1
What is equation for q?
q = m c △T
q = heat change in the reaction in Joules
m = mass of the water in grams
c = specific heat of water (4.2)
∆T = temperature change in the water in Kelvins
What method is used to measure calorimetric value?
Bomb calorimeter
What is standard enthalpy change of combustion and endo or exo?
The enthalpy change which occurs when 1 mole of a substanceis completely burnt in oxygenat 298K and 100kPa, with all substances in standard states
Always exo
What is standard enthalpy change of formation and endo or exo?
The enthalpy change which occurs when 1 mole of a substance is formed from its elements at 298K and 100kPa, with all substances in standard states
Can be both exothermic or endothermic
Equation for enthalpy change of formation?
△H = product - reactants
Equation for enthalpy change of combustion?
△H = reactants - products
Equation for bond enthalpy?
∆H = E1 + E2
What is bond dissociation enthalpy?
The enthalpy change when 1 mole of a specific bond in a specific gaseous molecule is broken at 298 K and 100 kPa
What is mean bond enthalpy?
The average amount of energy needed to break a covalent bond averaged over a range ofgaseous compounds at 298 K and 100 kPa
Is energy needed to break bond exo or endo?
Endothermic
Is energy needed to form bond exo or endo?
Exothermic
What is ionization energy?
1 mole of electrons are removed from 1 mole of gaseous particles
What is ionization energy?
1 mole of electrons are removed from 1 mole of gaseous particles
What is lattice enthalpy?
1 mole of an ionic solid is made from its gaseous ions
What is hydration enthalpy?
1 mole of gaseous ions is hydrated into 1 mole of aqueous ions
What is enthalpy of solution?
1 mole of a substance is dissolved in a large excess of water
Equation for enthalpy of solution?
∆Hsol = ∆HL.D. + ∑∆Hhyd
What is entropy of a system?
Measure of the disorder inside it
What is entropy of a system?
Measure of the disorder inside it
Gibbs energy equation?
ΔG = ΔH – TΔS
