Smartwork

The melting point of a substance is the temperature at which the particles have enough ______ energy to break free from the ______ phase and enter the ______ phase.

kinetic, solid, liquid

The study of reaction rates is called ____. This branch of chemistry studies _____ reactants are converted into products.

kinetics; how fast

Unlike most other substances, the density of solid H2O is than the density of the liquid; hence water when it freezes. This is reflected in the phase diagram for H2O (shown). The solid-liquid boundary line slopes upward to the , reflecting the fact that the higher the pressure the the temperature at which the water freezes.

less, expands, left, lower

A solute that has essentially no vapor pressure in comparison to the solvent is called a(n) solute.

nonvolatile

The triple point is represented on a phase diagram to show when all three ______ of a substance are at ______.

phases, equilibrium

A(n) ______ solution contains the maximum amount of solute that will dissolve in a given solvent at a particular temperature; a(n) ______ solution contains less than this amount of solute.

saturated; unsaturated

Which of the following statements correctly defines colligative properties?

Properties of a solution that depend only on the number of dissolved solute particles

Which of the following statements correctly describe the relationship between reaction rate and concentrations of reactants and products? Select all that apply.

Reactants (or products) with large coefficients have relatively high rates of disappearance (or appearance). Reactants (or products) with the same coefficient have the same rates of disappearance (or appearance).

If t represents time, the notation Δt should be interpreted as the _____.

change in time

Reaction rate is expressed as a change in the of reactants or products as a function of .

concentration; time

The solubility of a gas in water usually _____ with increasing temperature.

decreases

The rate of a reaction generally ____ over time as reactants are consumed. The average reaction rate calculated for the time interval t = 0.0 s and t = 10.0 s will therefore be ____ the average rate calculated for the time interval t = 0.0 s and t = 20.0 s.

decreases; greater

A solution forms when the attractive between the solute and solvent are in strength to the solvent-solvent and solute-solute attractions and are therefore able to replace them.

forces; similar

A 1.0 M solution of NaCl will have colligative properties of magnitude than a 1.0 M solution of glucose. This is because the NaCl solution has a(n) concentration of solute particles than the glucose solution.

greater; higher

The term "like dissolves like" reflects that fact that two substances will tend to form a solution if they have similar ______.

intermolecular forces

True or false: The calculated average rate of a reaction usually depends on the time interval chosen.

True

In a solution, one or more is/are dissolved in a(n) .

solute; solvent

For the reaction A → B, which of the following equations correctly express the reaction rate at time t? Select all that apply.

rate = Δ[B]/Δt rate = - Δ[A]/Δt

Which units may be used to express the reaction rate? Select all that apply.

atm/min M/s

Freezing point _____ is observed for solutions containing the appropriate solute. The vapor pressure of a solution is _____ than that of the pure solvent and the solution therefore freezes at a _____ temperature.

depression; lower; lower

Which of the following options correctly expresses the rate of the general reaction shown below in terms of the change in concentration of each of the reactants and products? A(g) + 2B(g) → C(g)

- Δ[A]/Δt = - 1/2 Δ[B]/Δt = Δ[C]/Δt

For most gases, what effect does temperature have on their solubility?

Most gases become less soluble as temperature increases.

Match each of the following solutes to the correct expected value for i, assuming ideal behavior in aqueous solution.

NH4Br -> i=2 C12H22O11 -> i=1 Na2CO3 -> i=3 AlCl3 -> i=4

Which of the following statements correctly describe melting and melting point? Select all that apply.

Pressure changes have little effect on the melting point of a substance. At the melting point of a substance the solid and liquid phases are in equilibrium.

What is the effect on vapor pressure of dissolving a nonvolatile solute in a given solute?

The vapor pressure of the solution will be lower than that of the pure solvent.

Which of the following options correctly describe molality? Select all that apply.

To calculate molality, the mass of solvent is needed. Molality is defined as: molesofsolutemassofsolvent(inkg)molesofsolutemassofsolvent(inkg).

The symbol Δ in a mathematical equation indicates _____. (Select all that apply.)

difference between values change in a value

An ionic solute dissolved in water would exhibit primarily ______ forces, while a solution of two hydrocarbons such as hexane (C6H14) and octane (C8H18) would exhibit primarily ______ forces.

ion-dipole; dispersion

A solution of a nonvolatile solute in a given solvent will always freeze at a _____ temperature than the pure solvent. This is due to the solution having a(n) ______ vapor pressure than the pure solvent.

lower; lower

In the phase diagram shown, the roughly vertical line marking the solid-liquid boundary slants to the right with increasing pressure. This indicates that the solid phase is ______ dense than the liquid phase.

more

Which of the following options correctly express the rate of the given reaction in terms of reactant and product concentrations? Select all that apply. 2ClO(g) → Cl2(g) + O2(g)

rate = Δ[Cl2]/Δt rate = - 1/2Δ[ClO]/Δt

Which of the following statements correctly describe freezing point depression for a solution? Select all that apply.

ΔTf is a positive value. Freezing point depression is proportional to the molality of the solution. The freezing point constant Kf is characteristic of the solvent.

Calculate the mole fraction of KBr (molar mass 119.00 g/mol) in a solution made by dissolving 0.30 g KBr in 0.400 L of H2O (d = 1.00 g/mL; molar mass 18.02 g/mol).

1.14 x 10-4

Calculate the expected boiling point of a solution containing 0.72 mol of MgCl2 in 1.00 kg of H2O, if Kb = 0.512oC⋅kg/mol.

100.0oC + (2.16 × 0.512) = 101.1oC

For the reaction 2A → B, which of the following statements best describes the relationship between the rates of change of reactants and products? Select all that apply.

A is used up twice as fast as B forms. The rate of decrease of A is equal to the rate of increase of B multiplied by two.

Which of the following statements correctly describe crystallization and/or precipitation? Select all that apply.

Both crystallization and precipitation describe the separation of excess solid substance from a supersaturated solution. Crystallization is the process in which dissolved solute comes out of solution and forms crystals.

Which of the following statements correctly describe chemical kinetics? Select all that apply.

Chemical kinetics is the study of reaction rates. Chemical kinetics measures how fast reactants are converted into products.

______ properties of solutions depend only on the number (or concentration) of particles in solution, not their identity.

Colligative

Match each of the following solutes to the correct expected value for i, assuming ideal behavior in aqueous solution.

HCl -> i=2 C6H12O6 -> i=1 MgCl2 -> i=3

Which expression of concentration takes the volume of the solution into account?

Molarity

Which of the following is the most significant drawback of using molarity vs. molality as a measure of solution concentration?

Molarity can change with solution temperature.

Which of the following statements correctly interpret the phase diagram shown? Select all that apply.

The arrow marked 1 represents a change from the solid to the liquid phase. The normal boiling point of this substance is 135oC.

How does the presence of a strong electrolyte in solution affect the colligative properties of a solution when compared to the same number of moles of a nonelectrolyte solute?

The electrolyte dissociates or ionizes to give a larger number of moles of dissolved particles, with a greater effect on the colligative properties.

Both soaps and cell membranes rely on the behavior of molecules with dual polarity. Which of the following statements correctly describe this behavior? Select all that apply.

The lipid molecules that make up a cell membrane have a nonpolar hydrocarbon portion and a polar-ionic "head." A soap functions because the nonpolar "tails" of the molecules bond to grease and the polar "heads" carry the grease into the solvent. A cell membrane maximizes contact between parts of the lipid molecules that form the most similar types of intermolecular forces.

What does it mean if two substances are described as miscible?

The substances are completely soluble in each other at any concentration.

Which of the following statements correctly describe sublimation? Select all that apply.

The tendency of a molecular substance to sublime is related to the strength of its intermolecular forces. Sublimation is the change from the solid directly to the gas phase. Nonpolar molecular substances are more likely to sublime than polar substances.

In a given reaction, the rate may be expressed as either rate = - Δ[Y]ΔtΔ[Y]Δt, or as rate = Δ[X]ΔtΔ[X]Δt. What must be true about X or Y if the reaction is proceeding in the forward direction? Select all that apply.

X is a product. Y is a reactant.

A solution of a nonvolatile solute in a given solvent will always have a _______ vapor pressure than the pure solvent. Thus the solution will boil at a _______ temperature than the pure solvent.

lower; higher

In general, ΔHofus is _____ than ΔHovap for a given substance because it takes _____ energy to overcome the forces holding the molecules in fixed positions (i.e., melt the substance) than to separate the molecules completely from each other (i.e., vaporize the substance

lower; less

The ratio molofsolute/Lofsolution is called the _____ of a solution (symbol M), whereas the _____ (symbol m) of the solution is expressed as molofsolute/kgofsolvent. For an aqueous solution, these two quantities will be very similar if the solution concentration is _____.

molarity; molality; low

Mole fraction expresses the concentration of a solution as a ratio of ______.

moles to moles

Which expression correctly represents the molality, m, of a solution?

molesofsolute/massofsolvent(in kg)

A semipermeable membrane is a barrier that allows ______ molecules/particles to pass through, but not ______ molecules/particles.

solvent; solute

If a pure solvent is separated from a solution by a semipermeable membrane, solvent particles will pass through the membrane from the _____ to the _____. This process is called osmosis and the _____ pressure (π) is the pressure that must be applied to stop the net flow of solvent.

solvent; solution; osmotic

The process in which a substance passes directly from the solid to the vapor phase is called . The reverse process is called

sublimation; deposition

A phase diagram is a plot of ______ on the x-axis vs. ______ on the y-axis. This diagram shows the stable regions for each ______ of matter and the conditions under which these may exist in equilibrium.

temperature, pressure, phase

A solution that contains the maximum amount of dissolved solute in a fixed quantity of solvent at a particular is called a(n) solution.

temperature; saturated

Which of the following options most accurately defines a solution?

A homogeneous mixture of two or more substances.

Which of the following options correctly describe a hydrophilic colloid? Select all that apply.

A hydrophilic colloid interacts with water via ion-dipole forces or hydrogen bonding. A hydrophilic colloid interacts favorably with water.

If two solutions are separated by a semipermeable membrane, the initial concentration of each may be the same or different. Match each term used to describe the pair solutions to the correct description.

Isotonic -> Two solutions are of equal concentration and have the same osmotic pressure Hypertonic -> The more concentrated solution when two solutions are of unequal osmotic pressure Hypotonic -> The less concentrated solution when two solutions are of unequal osmotic pressure

Which of the following statements correctly describe the molality and molarity of a solution? Select all that apply.

M must be calculated using the volume of the solution, not the volume of the solvent. Both molarity and molality express concentration in terms of moles of solute. For a dilute aqueous solution molality and molarity are nearly equal.

Match each concentration term with the correct ratio each represents.

Molarity (M) matches Choice, molofsoluteLofsolution molofsoluteLofsolutionmolofsoluteLofsolution Molality (m) matches Choice, molofsolutekgofsolvent molofsolutekgofsolventmolofsolutekgofsolvent Parts by mass matches Choice, massofsolutemassofsolution massofsolutemassofsolutionmassofsolutemassofsolution Mole fraction (X) matches Choice, molofsolutetotal#ofmolespresent molofsolutetotal#ofmolespresent

Which of the following options correctly describe mole fraction? Select all that apply.

Mole fraction is not affected by the temperature of the solution. The mole fraction of a component A is given by molesA/sumofmolesofallcomponents

Which answer choice correctly expresses the van't Hoff factor for a solute?

Molesofparticlesinsolution/Molesofsolutedissolved

______ pressure is the pressure necessary to stop diffusion of water across a semipermeable membrane from a solution of low solute concentration to a solution of high solute concentration.

Osmotic

Which of the following statements correctly describe Henry's law for gases? Select all that apply. c = kP

P is the partial pressure of the gas in the system. This law shows that the solubility of a gas increases with pressure. c is the solubility of the gas at a particular temperature.

An increase in pressure will cause the solubility of a gas to _____, whereas the solubility of a liquid or solid will usually _____.

increase; not change much

Which of the following are necessary components of a solution? Select all that apply.

Solvent One or more solutes

Which of the following options correctly describe the different ways of expressing the concentration of a solution? Select all that apply.

The unit for molality (symbol m) is mol/kg. To calculate mole fraction for a given mass of a reactant or product, the masses of all solution components must be known.

Which of the following options correctly describe the van't Hoff factor for the solution of an electrolyte? Select all that apply.

The van't Hoff factor is predicted from the number of particles the electrolyte will form after dissociation. The van't Hoff factor is used to predict the colligative properties of an electrolyte solution. The van't Hoff factor is greater than 1 for electrolyte solutions.

Match each term describing solutions with the correct definition. Unsaturated, Saturated, Supersaturated

Unsaturated matches Choice, a solution that contains less than the maximum amount of dissolved solute; more solute added will dissolve a solution that contains less than the maximum amount of dissolved solute; more solute added will dissolve Saturated matches Choice, a solution containing the maximum amount of dissolved solute; more solute added will not dissolve a solution containing the maximum amount of dissolved solute; more solute added will not dissolve Supersaturated matches Choice, a solution containing more than the maximum amount of solute; the solution is unstable and solute will separate from it readily a solution containing more than the maximum amount of solute; the solution is unstable and solute will separate from it readily

A solution contains 16.5 g naphthalene (C10H8; molar mass = 128.16 g/mol) in 53.3 g of benzene (C6H6; molar mass = 78.11 g/mol). Select all the options that show the correct calculations required to determine the mole fraction of naphthalene.

Xnapthalene = 0.1290.8110.1290.811 = 0.159 moles of benzene = 0.682 mol

Nitrogen and oxygen combine in the atmosphere to form NO, as indicated by the balanced equation below. N2(g) O2(g) → 2NO(g) The rate at which O2 is consumed is ____ the rate at which N2 is consumed, and is ____ the rate at which NO is produced.

equal to; half

A solution containing a nonvolatile solute always boils at a _____ temperature than the pure solvent. The vapor pressure of the solution is _____ than the vapor pressure of the pure solvent; hence the solution must be heated to a _____ temperature in order for the vapor pressure to equal the external pressure.vv

higher; lower; higher

Match each type of intermolecular force correctly to the type of solution in which each is exhibited.

ion-dipole forces matches Choice, An ionic solute in a polar solvent An ionic solute in a polar solvent ion-induced dipole forces matches Choice, A nonpolar solute in a polar solvent that also contains dissolved ions A nonpolar solute in a polar solvent that also contains dissolved ions dipole-induced dipole forces matches Choice, A nonpolar solute in a polar solvent A nonpolar solute in a polar solvent dispersion forces matches Choice, Present in all solutions; principal intermolecular force when both solvent and solute are nonpolar Present in all solutions; principal intermolecular force when both solvent and solute are nonpolar

In general the vapor pressure of a solution containing a nonvolatile solute is _____ than that of a pure solvent. The difference in vapor pressure is mainly due to the _____ amount of disorder in a solution.

less; increased

A nonvolatile solute is one that has a relatively _____ vapor pressure at the boiling point of the solvent.

low

A saturated solution of a gas in a liquid (in a closed system) is at equilibrium with a fixed number of gas molecules leaving and entering the solution every second. If the pressure on the system is increased, _____ molecules of gas strike the surface of the liquid and therefore _____ molecules of gas dissolve in the liquid. A gas is therefore _____ soluble at higher pressures.

more; more; more

The rate of a reaction is expressed as Δ[A]/Δt. If A is a reactant, a _____ sign must be added in front of this expression in order for the rate to have a _____ value. This is not necessary if A is a product.

negative; positive

Consider the solubility of Na2SO4(s) and O2(g) in water. A large change in atmospheric pressure will have a ______ effect on the solubility of Na2SO4, and a ______ effect on the solubility of O2.

negligible; significant