GR12- unit 5 thermochemistry unit test

kinetic energy

energy of motion of particles of a laboratory scale

potential energy

energy an object possesses as a result of its position in space or condition

thermal energy

an example of kinetic energy, due to the motion of particles

temperature

measure of the average kinetic energy of particles

what is a system, surroundings, and thermodynamic universe

system= what we’re looking at

surroundings= everything else

thermodynamic universe= system + surroundings 

heat

energy transferred from a hotter object to a colder one

types of systems

open system= matter and energy can enter and leave the system freely

closed system= only energy can leave and enter the system

isolated system= neither matter or energy can leave the system

endothermic

energy added to system (IN)

exothermic

energy leaving the system (EXIT)

EQN for calorimetry formula

q=mc△T

enthalpy

the total amount of thermal energy

it is difficult to measure the absolute amount of thermal energy, however, the energy change can be measured using calorimetry

EQN for molar enthalpy change reactions (EX: △Hsol, △Hcomb…)

△H= n△Hr (where r is changed depending on reaction)

bond dissociation energy

energy required to break a chemical bond

EQN for bond dissociation energy

△H= ∑n x D_{bonds broken} - ∑n x D_{bonds formed}

Hess’ Law

the enthalpy change for the conversion of reactants to products is the same whether the conversion occurs in one step or multiple

what are the rules for enthalpy changes in Hess’ Law

1. if you reverse the equation, reverse the sign of △H

2. if you multiply the equation by a coefficient, multiply △H as well

how do you add the chemical equations using Hess’ Law?

1. if 2 identical substances are on opposite sides of the arrow, cancel them out (only if the coefficients are the same, if not, subtract)

2. if 2 identical substances are on the same side of the arrow, add their coefficients together 

3. keep substances left over in the final equation 

what are the SATP conditions?

T= 298.15 K

P= 1.oo atm

EQN for standard enthalpy of formation 

△Hr= ∑n_products△H_fproducts - ∑n_reactants△H_freactants