Chem1040 Final Exam

All Units

Intermolecular forces are all weaker than ____________ bonds.

ionic

Define intermolecular forces.

Attractive forces between neighboring molecules.

Intermolecular forces determine properties like __________ and viscosity.

boiling point

Intermolecular forces that work between atoms of pure substances are called

Van der Waals forces

_______________ occur within polar molecules between partial positive and partial negative sides.

Dipole-dipole interactions

The weakest IMFs are

dispersion forces

_______________ occur because of attractions at instantaneous dipole.

Dispersion forces

_______________ attraction occurs between a polar molecule and an ion found in solution (when combining polar molecule + ionic compound).

Ion-dipole

An __________ is a special type of dipole-dipole that occurs only in molecules with H bonded directly to a small, electronegative atom. Give the 3 atom possibilities.

H-bond- N, O, F

the stronger the intermolecular forces, the _______ the boiling point

higher

A solution is made up of

solute (usually smaller quantity) and solvent (usually larger quantity)

A solution is a _________ mixture.

homogeneous

An ________ solution can dissolve more solute.

unsaturated

A ____________ solution is one in which the maximum amount of solute has been dissolved.

saturated

A ____________ solution is very unstable, and solute easily precipitates out if solution is disturbed.

supersaturated

________________ is the amount of solute dissolved in a given volume of solution at a specific temperature.

Solubility

A solution can only form if ________ interactions are stronger than _______ interactions.

solute-solvent, solute-solute/solvent-solvent

An_________ process of solution formation requires input of energy to overcome intermolecular forces.

endothermic

Separating solute molecules from one another and solvent molecules from one another is ____________.

endothermic

Mixing solute and solvent together, when energy is given off, is ____________

exothermic

An ____________ process of solution formation releases energy.

exothermic

Entropy

a measure of how spread out the energy of a system is

The process by which solute particles are surrounded by solvent molecules is

solvation

The concept of "like dissolves like" is also known as

miscibility

The units of molarity are

mol solute/L solution (M)

Mole fraction equation

X= mol A/ sum of total mol

The units of molality are

mol solute/ kg solvent

Percent by mass of a solute is

mass solute/ mass solution x 100%

Volume=

mass/density

As temperature increases, gases become _________ soluble.

less

As temperature increases, solids become ________ soluble.

more

As pressure increases/ volume decreases, gases become _________ soluble.

more

As pressure increases/volume decreases, solids become _________ soluble.

trick question- unchanged solubility

Colligative properties depend on

number of dissolved particles

With a greater number of particles in solution, the solution will have __________ freezing point than pure solvent.

lower

With a greater number of particles in solution, the solution will have ____________ boiling point than pure solvent.

higher

With a greater number of particles in solution, the solution will have ____________ vapor pressure than the pure solvent.

lower

With a greater number of particles in solution, the solution will have __________ osmotic pressure than the pure solvent.

higher

A volatile substance has

measurable vapor pressure

A nonvolatile substance has

vapor pressure that cannot be measured

The flow of solvent through a semipermeable membrane (allows solvent but not solute to pass) from a more dilute to a more concentrated solution.

osmosis

The pressure required to keep osmosis from occurring is

osmotic pressure

Isotonic solutions have _________ osmotic pressure.

the same

Hypotonic solution has ___________ osmotic pressure.

lower

Hypertonic solution has __________ osmotic pressure.

higher

The number of dissolved particles in electrolyte solutions is decreased because of _________ or ______________. We account for this using __________.

dissociation or ionization; i (Van't Hoff factor)

Experimental i is usually ___________ than the calculated value. Why?

smaller; due to ion pair formation

The Van't Hoff factor indicates

degree of dissociation or ionization of an electrolyte

______________ is a dispersion of particles of one substance throughout another substance.

A colloid

When a beam of light passes through a colloid, it is scattered by the dispersed phase. This is called the

Tyndall effect

Hydrophilic colloids contain

large molecules like proteins

Hydrophobic colloids

Not normally stable in H2O, stabilized by adsorption of ions to their surface

A process that does occur under a specific set of conditions is a

spontaneous process

A ball rolling downhill is an example of a __________ process.

spontaneous

A process that does not occur under a specific set of conditions is a

nonspontaneous process

A ball rolling uphill is an example of a _____________ process.

nonspontaneous

Spontaneous processes are often _________ and ___________ energy. They tend to have a ________ delta H value.

exothermic, give off, - Delta H

Nonspontaneous processes are often __________ and _____________ energy. They tend to have a ________ delta H value.

endothermic, require, + Delta H

T/F: The sign of delta H is not sufficient to determine spontaneity.

True

To predict spontaneity we need to know: 1. ______________ and 2. ________________

1. delta H (enthalpy) 2. delta S (entropy)

____________ is a measure of how spread out/ dispersed the system's energy (dispersal of motional energy).

Entropy (S)

Higher entropy favors ____________.

spontaneity

The most probable state is the one with the __________ # of possible arrangements.

largest

An increase in volume means that entropy (S) ______________.

increases.

An increase in temperature means that entropy (S) ______________.

increases

An increase in molecular complexity means that entropy (S) _______________.

increases.

An increase in molar mass means that entropy (S) ________________.

increases

Entropy (S) ____________ when a substance is melted (s => l), vaporized (l => g) or sublimed (s => g).

increases

Entropy (S) _____________ when a substance is frozen (l=> s) or condensed (g => l).

decreases

Gases have the ____________ molecular motion, then ___________, then ___________.

greatest, liquid, solid (have least MM)

The system is the

part of the universe we are investigating

The surroundings are

everything beside the system

When an ice cube melts spontaneously, what is the delta S of the system? What is the delta S of the surroundings? Why?

Delta S system + (required energy input from surr.)
Delta S surroundings - (released heat to system, endothermic rxn)

When hot water cools spontaneously, what is the delta S of the system? What is the delta S of the suroundings? Why?

Delta S system - (heat lost from water)
Delta S surroundings + (heat goes to surroundings, exothermic)

Entropy change of the universe is _____________ for spontaneous processes and ________ for equilibrium processes. This is called the _________________.

positive, 0
Second Law of Thermodynamics

Entropy of a perfect crystalline substance at 0K is equal to 0. This is called the

Third Law of Thermodynamics

What is Delta G?

Gibbs free energy

If 0 > Delta G, the reaction is ____________ in the forward direction and _______________ in reverse.

spontaneous, nonspontaneous

If Delta G > 0, the reaction is _____________ in the forward direction and ___________ in reverse.

nonspontaneous, spontaneous

If Delta G is equal to 0, the system is at

equilibrium

With a -H, +S, -G, the process is

always spontaneous

With +H, -S, +G, the process is

always nonspontaneous

With -H, -S, varying delta G, the process is

spontaneous at low temp, nonspontaneous at high temp

With +H, +S, varying delta G, the process is

nonspontaneous at low temp, spontaneous at high temp

___________ is the free energy change for a rxn under standard state conditions (gases 1 atm, pure liquid, pure solid, most stable form of element, 25 degree C, 1 M solution, etc.).

Delta G naught of reaction

Thermodynamically favorable reactions provide free energy needed to drive ________________ in the body.

necessary but thermodynamically unfavorable

In a forward reaction, reactants are ____________ and products are ___________.

consumed; produced

In a reversible process, products can

also be consumed to form reactants, in addition to being produced.

______________ occurs when the forward and reverse reactions are occurring at the same rate and there is not net change in reactant/ product concentrations over time.

Equilibrium

Qc is the _____________ and Kc is the _____________.

reaction quotient, equilibrium constant

Kc is ____________ at constant temperature. If Kc is greater than 100, ____________ are favored at equilibrium. If Kc is less than 0.01, ___________are favored at equilibrium.

constant
products
reactants

Heterogenous equilibria occurs when

species in the reaction are not all in the same phase- we omit the solid and liquid concentrations from Kc expression.

In gaseous equilibria, we can write an alternate form of the expression in which concentrations are represented by

partial pressures (in atm)

If K is large and -delta G, reaction is _________________ . At equilibrium, there are mostly _____________.

spontaneous, products

If K is very small and delta G is positive, reaction is _____________. At equilibrium, there are mostly _____________-.

nonspontaneous, products

If Q < K, the reaction will proceed _____________. We need __________ to convert to ____________ in order to reach equilbrium.

forward, Reactants => products

If Q=K, the reaction is

already at equilibrium

If Q > K, the reaction will proceed _______________. We need __________ to convert to _____________ in order to reach equilibrium.

in reverse, products => reactants

If K is greater than 1 and delta G is -, ___________ formation is favored at equilbrium

product

If K is equal to 1 and delta G is 0, _____________ formation is favored at equilibrium.

neither product/reactant (already at equilibrium)