Thermodynamics 2
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Define heat capacity
The amount of heat required to raise the temp of an object or substance a given amount
Give the equation to calculate quantity of heat with Heat Capacity (C)
q = C x change in temp
Define molar heat capacity
The amount of heat required to raise the temp of 1 mol of a substance by 1 degrees C
Give the equation to calculate q with molar heat capacity.
q = (Cm) x (moles of substance) x change in temp
Define specific heat
The amount of heat required to raise the temperature of 1 g of a substance by 1 °C.
Give the equation to calculate q using specific heat
q = (specific heat) x (mass of substance) x ∆T
What is Hess’s law?
The overall enthalpy change for a reaction is equal to the sum of enthalpy changes for the individual steps in the reaction.
Give the equation for the haber process.
3H2(g) + N2(g) 2NH3(g)
Define standard enthalpy of formation
The heat change that results when one mole of a compound is formed from its elements at a pressure of 1 atm in their STANDARD STATES
Define standard HEAT of formation.
The enthalpy change for the formation of 1 mol of a substance in its standard state from its constituent elements in their standard states.
What is the value of an element at its most stable form?
zero
Give the equation for the fermentation of glucose under standard conditions.
C6H12O6(s) ➞ 2 C2H5OH(l) + 2 CO2(g) ΔHo = -72 kJ
what kind of process is breaking bonds?
endothermic
What kind of process is making new bonds?
Exothermic
Define bond dissociation energy.
The amount of energy that must be supplied to break a chemical bond in an isolated molecule in the gaseous state and is thus the amount of energy released when the bond forms.
How to calculate bond enthalpies.
Reactants - products
How to calculate standard reaction enthalpy?
ΔrHo = ΣνH o(products) - ΣνH o(reactants)
What is meant by state function?
A function or property whose value depends only on the present state, or condition, of the system, not on the path used to arrive at that state.
Define enthalpy change.
The heat change in a reaction or process at constant pressure; ΔH= ΔE+ PΔV.
Define entropy.
The amount of molecular randomness in a system.
What are spontaneous processes favoured by?
favored by a decrease in H (negative ∆H). favored by an increase in S (positive ∆S).
What are non spontaneous processes favoured by?
favored by an increase in H (positive ∆H). favored by a decrease in S (negative ∆S).
How to calculate entropy change?
ΔS = Sfinal - Sinitial