CHE 130: Energy

1st Law of Thermodynamics:

energy cannot be created or destroyed, therefore energy is conserved in any process

What is temperature?

the measure of average kinetic energy,

higher temperature = more particle movement

Coulomb’s law as it applies to charges and radius?

higher charges of ions = stronger attraction,

smaller radius of ions = ions can get closer together

Specific heat equation per gram:

q = m C_s ΔT

Specific heat equation per mole:

q = n C_n ΔT

Variables in the specific heat equation:

q: heat (J)

m: mass (g) / n: moles (mol)

C_s: heat capacity (J/g°C) / C_n: heat capacity (J/mol°C)

ΔT: change in temperature (°K or °C)

Thermal energy transfer equations (q_hot and q_cold):

q_hot = - q_cold,

q_hot + q_cold = 0P

What are the properties and constant of a bomb calorimeter?

closed container, rigid walls, CONSTANT VOLUME

What are the properties and constant of a coffee cup calorimeter?

not sealed, CONSTANT PRESSURE

What is C_cal?

the heat capacity of a calorimeter, in (J/°C) or (J/°K),

sometimes ignored/set to 0

What equation to use with a bomb calorimeter?

ΔH_rxn = q_rxn / n_rxn ,

assumes volume constant and work = 0

When to use enthalpy?

under constant pressure conditions

Enthalpy reaction:

ΔH = q p

Enthalpy of endothermic reactions:

ΔH > 0,

process consumes energy, energy is a reactant

Enthalpy of exothermic reactions:

ΔH < 0,

process releases energy, energy is a product