Study your flashcards anywhere!

Download the official Cram app for free >

  • Shuffle
    Toggle On
    Toggle Off
  • Alphabetize
    Toggle On
    Toggle Off
  • Front First
    Toggle On
    Toggle Off
  • Both Sides
    Toggle On
    Toggle Off
  • Read
    Toggle On
    Toggle Off
Reading...
Front

How to study your flashcards.

Right/Left arrow keys: Navigate between flashcards.right arrow keyleft arrow key

Up/Down arrow keys: Flip the card between the front and back.down keyup key

H key: Show hint (3rd side).h key

A key: Read text to speech.a key

image

Play button

image

Play button

image

Progress

1/37

Click to flip

37 Cards in this Set

  • Front
  • Back

Definition: Thermochemistry

The study of the relationships between chemistry and energy

Definition: Energy

The capacity to do work

Definition: Work

Force acting through a distance

Definition: Heat

The flow of energy caused by a temperature difference (high to low)

Definition: Kinetic energy

Energy associated with motion

Definition: Thermal energy

Energy associated with temperature (a type of kinetic energy)

Definition: Potential energy

Energy associated with position or composition

Definition: Chemical energy

Energy associated with the relative positions of electrons and nuclei in atoms and molecules (a type of potential energy)

Definition: System

The portion of the universe that is singled out for investigation

Definition: Surroundings

Everything outside of the system

Units of energy

joule (J) = 1kg m^2/s^2


calorie (cal), the energy it takes to raise 1g of water 1°C = 4.184 J


Calorie (C) = 1000 cal


kilowatt-hour (kWh) = 3.60 x 10^6 J

Formula for change in energy of a reaction

ΔE = Eproducts - Ereactants


ΔE is negative when the reaction gives off energy


ΔE is posative when the reaction absorbs energy

Relationship between ΔEsys and ΔEsurr

ΔEsys = -ΔEsurr

Two factors that make up change in energy

ΔE = heat transferred + work done


ΔE = q + w

Definition: Thermal equilibrium

When heat transfer stops because the substances have reached the same temperature

Definition: Heat capacity

Symbol: C


The quantity of heat required to change the temperature of the system by 1°C

Formula for heat capacity

C = q/ΔT = J/°C


also know the arrangement of that, q = C x ΔT

Definition: Specific heat capacity

Symbol: Cs


Unit: J/g


The intrinsic capacity of a substance to absorb heat. The amount of heat required to raise the temp. of 1g of the substance by 1°C

Definition: Molar heat capacity

Unit: J/mol x °C


The amount of heat required to raise the temp. of 1 mol of a substance by 1°C

Heat capacity is a _______ property


Specific heat capacity and molar heat capacity are _______ properties

extensive (depends on how much is being heated)


intensive (a constant for that substance)


Formula for heat using specific heat capacity

heat = mass x specific heat capacity x temp. change


q = m x Cs x ΔT

Relationship between qsys and qsurr

qsys = -qsurr

Formula for work

w = -pressure x change in volume


w = -P x ΔV


convert units from atm x L to J use the conversion factor 101.3 J = 1 atm x L

Formula for change in heat of a reaction at constant volume

ΔErxn = heat at constant volume


ΔErxn = qv

Definition: Calorimetry

A process in which we deduce the thermal energy exchanged between a reaction and the surroundings by measuring the change in temp. of the surroundings

Enthalpy means we are observing the system under constant _______

pressure
i.e. how we feel about chem class

Formula for enthalpy

Symbol: H


H = E + PV

Formula for change in enthalpy

ΔH = heat at constant pressure


ΔH = qp

The difference between ΔE and ΔH

ΔE represents change in heat and work


ΔH just represents change in heat

Definition: Exothermic reaction

A reaction that gives off heat to its surroundings

Definition: Endothermic reaction

A reaction that absorbs heat from its surroundings

Standard states by state of matter

Gas: pure gas at pressure of 1 atm


Liquid or Solid: pure in its most stable form at 1 atm and the temp. of interest (usually 25°C)


Substance in solution: at concentration of 1M

Definition: Standard enthalpy change

Symbol: ΔH°


The change in enthalpy for a process when all reactants and products are in their standard states (that's what the ° means)

Definition: Standard enthalpy of formation / standard heat of formation

Symbol: ΔH°f


For a pure compound: The change in enthalpy when one mol of the compound forms from its constituent elements in their standard states.


For a pure element in its standard state: ΔH°f = 0

Definition: Decomposition

When a compound breaks down into it's constituent elements in their standard states. Reverse the sign on ΔH°f

Rules for ΔHrxn in chemical equations

1. If the equation is multiplied by a factor, multiply ΔHrxn by the factor

2. If the equation is reversed ΔHrxn changes sign


3. If an equation is the sum of a series of steps the the ΔHrxn for the overall rxn is the sum of the ΔHrxn's for each step

To calculate the ΔH°frxn

Subtract the enthalpies of formation of the reactants multiplied by their stoichiometric coefficients from the enthalpies of formation of the products multiplied by their stoichiometric coefficients.


ΔH°frxn = ∑npf(products) - ∑nrf(reactants)