Chapter 8 - Thermodynamics and Thermochemistry

What is the first law of thermodynamics?

Energy cannot be created or destroyed. It can only be transformed or transferred from one location to another

In regards to the law of thermodynamics, what two components make up the universe?

Universe = system + surroundings

The term universe can be refered to as?

the sum of the system and its surroundings

The term system can be refered to as?

the chemical reaction containing reactants and products

The term syrroundings can be refered to as?

the environment that surrounds the system

What is enthalpy?

Amount of heat energy contained within a system

What is a state function?

A property whose value only depends on the initial and final states of the system

What is a path function?

A property that depends on the transition of a system from the initial to the final state

Is heat a state or path function?

Path function

What is the formula for calculating change in enthalpy?

ΔH = Hproducts (enthalpy of products) - Hreactants (enthalpy of reactants)

What is an endothermic reaction?

A process in which heat is transferred from surroundings to the system (surroundings will feel cold)

What is the change in enthalpy for an endothermic processes?

ΔH > 0 The change in enthalpy for the system is greater than 0. Absorbs heat from the surroundings.

What is an exothermic reaction?

A process in which heat is transferred from system to the surroundings

What is the change in enthalpy for an exothermic processe?

ΔH < 0 The change in enthalpy for the system is less than 0. Releases heat to the surroundings.

The transition from solid to gas, is it exothermic or endothermic?

Endothermic

The transition from gas to liquid, is it exothermic or endothermic?

Exothermic

The transition from liquid to gas, is it exothermic or endothermic?

Endothermic

The transition from liquid to solid, is it exothermic or endothermic?

Exothermic

The transition from solid to liquid, is it exothermic or endothermic?

Endothermic

The transition from gas to solid, is it exothermic or endothermic?

Exothermic

Is sublimation endothermic or exothermic?

Endothermic

Is deposition endothermic or exothermic?

Exothermic

Is vaporization endothermic or exothermic?

Endothermic

Is condensation endothermic or exothermic?

Exothermic

Is melting endothermic or exothermic?

Endothermic

Is freezing endothermic or exothermic?

Exothermic

What term describes the transfer of heat via direct contact?

Conduction

What term describes the transfer of heat via motion of liquid or gas?

Convection

What term describes the transfer of heat via electromagnetic radiation?

Radiation

What is the equation of work using heat?

ΔE = q + w

What is the equation of work using pressure?

w = -PΔV

Positive work can be described as?

work done on the system (gas), resulting in an increase in energy and decrease in volume.

Negative work can be described as?

work done by the system (gas), resulting in a decrease in energy and increase in volume.

What is the definition of specific heat capacity (C)?

Amount of energy required to raise the temperature of one gram of a substance by one Celsius

What are the units for specific heat?

J/g°C.

Which phase of water has the highest specific heat capacity?

Liquid, at 4.18 J/g°C

What equation do we use to calculate the heat (q) a substance absorbs or releases and its mass (m)?

q = m x C x ΔT

What is the equation for calculating heat for phase changes?

q = mΔHfus/vap

Does forming bonds require or release energy?

Releases energy

Does breaking bonds require or release energy?

Requires energy

When you input energy to break bonds in a molecule, what changes relative to the energy state of the molecule?

The molecule is previously in a lower energy state, and after breaking bonds, forms a higher energy state (more unstable)

What is the heat of fusion defined as?

the heat required to change a substance from solid to liquid

What is the heat of vaporization defined as?

the heat required to change a substance from liquid to gas

What is a bomb calorimeter used for?

used to measure the heat of combustion of a substance, typically by burning it under an oxygen-rich atmosphere in a closed vessel. to measure the amount of heat produced by a chemical reaction.

What two equations are used for bomb calorimetry calculations?

qrxn = - qcal

qcal = CΔT

What is the formula for calculating enthalpy change based on bond energy?

ΔH°rxn= ∑ ΔH°Bonds broken (reactants) - ∑ΔH°Bonds formed (products)

What is the standard enthalpy of formation?

The change in enthalpy that happens when one mole of the substance is made in its standard state

What is the formula for calculating standard enthalpy of formation?

ΔH°rxn= ∑n ΔH°f(products) - ∑n ΔH°f(reactants)

What is the standard enthalpy of formation for elements in its standard state?

0

Based on Hess's law, if you reverse a positive enthalpy reaction, what happens to the enthalpy change for that reaction?

It becomes negative

Based on Hess's law, if you were to multiply an equation by a coefficient of three, what happens to the enthalpy change for that reaction?

It triples

Based on Hess's law, if you were to divide an equation by a coefficient of 2, what happens to the enthalpy change for that reaction?

It halves

Are atoms in a molecule always in motion?

Yes

The amount of disorder in a system is called what?

Entropy

What is the symbol used to represent entropy?

S

What is the second law of thermodynamics?

The entropy of the universe is always increasing (the universe is becoming more and more disordered).

What is the third law of thermodynamics?

The entropy of a pure crystalline substance at absolute zero temperature (0 Kelvin) is zero.

What is the formula for calculating the change in entropy in a given reaction?

ΔSrxn= ∑n S(products) - ∑n S(reactants)

A solid converting into liquid, is this positive or negatively entropic?

Positive (more disorder)

A gas undergoing deposition into a solid, is this positive or negatively entropic?

Negative (less disorder)

If you have a positive change in entropy for a reaction, what does this suggest?

Products are more disordered than reactants

If you have a negative change in entropy for a reaction, what does this suggest?

Reactants are more disordered than products

Is a positive or negative change in entropy favored?

Positive change in entropy is favored

If a chemical reaction results in an increase in gas molecules, then should change in entropy be positive or negative?

Positive

If a chemical reaction turns a solid reagent into an aqueous product, then should change in entropy be positive or negative?

Positive

Are all spontaneous reactions immediately occurring?

No, not necessarily. Spontaneous simply refers to any process that occurs without input of external energy

Is the conversion of diamond into CO2 considered spontaneous even though it may take billions of years tot occur?

Yes, as no input of energy is neeed

What is the formula for Gibbs free energy equation?

ΔG = ΔH - TΔS

If Gibbs' free energy is positive, are products or reactants favored at equilibrium?

Reactants

If Gibbs' free energy is negative, are products or reactants favored at equilibrium?

Products

Is entropy and enthalpy classified as

state functions or path functions?

State functions

Is work and heat classified as state functions or path functions?

Path functions