Chapter 11-12 Chem 2 FSW (Exam 1)

What happens when a solution forms?

A solution forms when two or more substances combine physically to yield a mixture that is homogeneous at the molecular level.

What is the solvent in a solution?

The most concentrated component and determines the physical state of the solution.

What are the solutes in a solution?

The other components typically present at concentrations less than that of the solvent.

When do ideal solutions form?

With no appreciable change in energy.

What are electrolytes?

Substances that dissolve in water to yield ions.

How do ionic electrolytes dissolve?

Ionic compounds that dissociate to yield their constituent cations and anions when dissolved.

How is the dissolution of an ionic compound facilitated?

By ion-dipole attractions between the ions of the compound and the polar water molecules.

What makes a strong electrolyte strong?

Soluble ionic substances and strong acids ionize completely.

What makes a weak electrolyte weak?

Weak acids and bases ionize to only a small extent.

What are nonelectrolytes?

Substances that do not produce ions when dissolved in water.

What determines the extent to which one substance will dissolve in another?

Factors including the types and relative strengths of intermolecular attractive forces that may exist between the substances’ atoms, ions, or molecules.

What is a substance's solubility?

Its maximum concentration in a solution at equilibrium under specified conditions.

What is a saturated solution?

Contains solute at a concentration equal to its solubility

What is a supersaturated solution?

One in which a solute’s concentration exceeds its solubility, resulting in solute precipitation when sufficiently perturbed.

What are miscible liquids?

Soluble in all proportions

What are immiscible liquids?

Exhibit very low mutual solubility.

How do solubilities change with temperature?

Decrease with increasing temperature, while those for most, but not all, solid solutes increase with temperature.

What is Henry's Law?

The concentration of a gaseous solute in a solution is proportional to the partial pressure of the gas to which the solution is exposed.

What are colligative properties?

Properties of a solution that depend only on the concentration of solute particles.

What changes are included in colligative properties?

Changes in the vapor pressure, boiling point, and freezing point of the solvent in the solution.

What is osmotic pressure?

The pressure that must be applied to the solution to prevent diffusion of molecules of pure solvent through a semipermeable membrane into the solution.

How do solutions differ from compounds?

Composition of solution can vary, while composition of compound cannot vary

what is the major force in NaCl aqueous solution?

ion-dipole

Choose the statement below that is TRUE:

A solution will form between two substances if the solute-solvent interactions are of comparable strength to the solute-solute and solvent-solvent interactions.

Identify the major force between molecules of pentane, CH3CH2CH2CH2CH3.

London dispersion

If two substances are soluble in all proportions then they are in each other.

miscible

Dissolving of a salt can be defined as

solvation of ions, with decrease in the amount of solid.

Define solubility.

the amount of a substance that will dissolve in a given amount of solvent

A solution containing less than the equilibrium amount is called

an unsaturated solution.

A solution is formed at room temperature by vigorously dissolving enough of the solid solute so that some solid remains at the bottom of the solution. Which statement below is TRUE?

The solution is considered saturated.

Which of the following statements is TRUE?

The solubility of a solid is highly dependent on temperature.

To increase solubility of a gas into a liquid the most, then

decrease the temperature and raise the pressure.

Which of the following statements is TRUE?

In general, the solubility of a gas in water decreases with increasing temperature.

Identify the compound whose solubility is least affected by temperature.

NaCl

Choose the statement below that is TRUE.

A weak acid solution consists of mostly nonionized acid molecules.

HBr, HI, HClO4, KBr, and KI are all classified as:

strong electrolytes.

Which of the following solutions will have the highest electrical conductivity?

0.045 M Al2(SO4)3

Identify barium hydroxide, Ba(OH)2.

strong electrolyte, strong base

Identify Nal.

strong electrolyte

Identify acetic acid, CH₃COOH.

weak electrolyte, weak acid

Give the term for the amount of solute in moles per liter of solution.

molarity

What are the colligative properties of a solution?

Vapor-Pressure Lowering
Boiling-Point Elevation
Freezing-Point Depression

Identify the solute with the lowest van't Hoff factor.

nonelectrolyte

Give the reason that antifreeze is added to a car radiator.

The freezing point is lowered, and the boiling point is elevated.

What is a spontaneous process?

A process that occurs without the need for continual energy input from an external source.

What is entropy (S)?

A state function related to the number of microstates for a system and the ratio of reversible heat to Kelvin temperature; it measures disorder/chaos in a system.

How does entropy relate to the phase of a substance?

Entropy increases as follows: Ssolid < Sliquid < Sgas.

What does the second law of thermodynamics state?

A spontaneous process increases the entropy of the universe, Suniv > 0.

What is the third law of thermodynamics?

It establishes the zero for entropy as that of a perfect, pure crystalline solid at 0 K.

Define Gibbs Free Energy (G)

The energy that may be converted into work in a system that is at constant temperature and pressure; it's used to predict the spontaneity of a process.

List the 3 critical factors in calculating the Gibbs free energy

Enthalpy, entropy, and temperature.

What is the equation to calculate standard entropy change?

ΔSo = Σ vs (products) - Σ vs (reactants)

What is the equation relating Gibbs free energy, enthalpy, entropy, and temperature?

ΔG = ΔH – TΔS

What happens to reaction spontaneity when ΔH is positive and ΔS is positive at low temperatures?

Nonspontaneous (ΔG > 0)

What happens to reaction spontaneity when ΔH is positive and ΔS is positive at high temperatures?

Spontaneous (ΔG < 0)

What happens to reaction spontaneity when ΔH is negative and ΔS is negative at low temperatures?

Spontaneous (ΔG < 0)

What happens to reaction spontaneity when ΔH is negative and ΔS is negative at high temperatures?

Nonspontaneous (ΔG > 0)

What happens to reaction spontaneity when ΔH is negative and ΔS is positive?

Spontaneous (ΔG < 0) at all temperatures

What happens to reaction spontaneity when ΔH is positive and ΔS is negative?

Nonspontaneous (ΔG > 0) at all temperatures

What equation is used to calculate standard Gibbs free energy changes (ΔG) from formation values?

ΔGreaction = ∑ ΔGf(products) − ∑ ΔGf(reactants)

When do you use the equation ΔG = ΔH − TΔS?

When under Non-Standard Conditions, if the temperature is not 298 K or if you are given specific values for ΔH and ΔS at a particular temperature, or When Temperature Effects Need to be Considered.

Which process is spontaneous: rusting of iron, electrolysis, browning of bread, photosynthesis, or frying an egg?

Rusting of iron

In which process do molecules become more orderly: water freezing, ice melting, ethanol evaporating, or salt dissolving in water?

Water freezing

Identify the process where entropy increases: gas to liquid, solid to gas, gas to solid, or liquid to solid.

The phase transition from a solid to a gas

Which change of state does NOT have an increase in entropy: water freezing, water boiling, ice melting, dry ice subliming, or water evaporating?

Water freezing

Which of the following processes has a ΔS > 0: SO2 (l) → SO2 (s), N2(g) + 3 H2(g) → 2 NH3(g), CH4(g) + H2O(g) → CO(g) + 3 H2(g), or K2CO3(s) + H2O(g) + CO2(g) → 2 KHCO3(s)?

CH4(g) + H2O(g) → CO(g) + 3 H2(g)

Which of the following processes has a ΔS < 0: ethanol freezes, 2-propanol (g, at 555 K) → 2-propanol (g, at 400 K), or carbon dioxide(g) → carbon dioxide(s)

All of the above processes have a ΔS < 0.

Arrange the following sets of systems in order of increasing entropy: H2O(l), H2O(g), H2O(s)

H2O(s) < H2O(l) < H2O(g)

Arrange the following sets of systems in order of increasing entropy: He(g), Cl2(g), P4(g)

He(g) < Cl2(g) < P4(g)

Which law of thermodynamics states that for any spontaneous reaction, the entropy of the universe increases?

Second

An exothermic reaction is a process that…

has a negative ΔHsys and a positive ΔSsurr.

Consider a reaction that has a positive ΔH and a positive ΔS. Which of the following statements is TRUE?

This reaction will be spontaneous only at high temperatures.

Consider a reaction that has a negative ΔH and a positive ΔS. Which of the following statements is TRUE?

This reaction will be spontaneous at all temperatures.

What is the standard free energy of formation for all elements?

Zero

What is the third law of thermodynamics?

The entropy of a pure, perfect crystalline substance at 0 K is zero

When sodium chloride is added to water and stirred, it dissolves spontaneously, and the resulting solution feels cold. What are the signs of ΔG, ΔH, and ΔS for this process?

ΔG negative, ΔH positive, and ΔS positive

When NaOH is added to water and stirred, it dissolves spontaneously, and the resulting solution feels hot. What are the signs of ΔG, ΔH, and ΔS for this process?

ΔG negative, ΔH negative, and ΔS positive

When ammonium nitrate (NH₄NO₃) is added to water, it dissolves spontaneously, and the solution becomes significantly colder. What are the likely signs of ΔG, ΔH, and ΔS for this process?

ΔG < 0, ΔH > 0, ΔS > 0

A chemical reaction is non-spontaneous at low temperatures but becomes spontaneous at high temperatures, absorbs heat, and produces more moles of gas than it consumes. What are the likely signs of ΔG, ΔH, and ΔS for this process?

ΔG changes sign with temperature, ΔH > 0, ΔS > 0