CHAPTER 12

What pressure of carbon dioxide is required to keep the carbon dioxide concentration in a bottle of club soda at 0.12 M at 25 °C?

3.5 atm

What volume (in mL) of a soft drink that is 10.5% sucrose by mass contains 78.5 grams of sucrose. The density of the sucrose is 1.04 g/mL.

718.86 mL

unsaturated solution

A solution that contains less solute than a saturated solution does and that is able to dissolve additional solute

Solute

A substance that is dissolved in a solution. minority substance in solution Ex: sodium Chloride

What is the effect of a nonvolatile, non-electrolyte solute on the vapor pressure of the liquid into which it dissolves?

The vapor pressure of the solution is lower than the vapor pressure of the pure solvent.

mole fraction

amount solute (in mol)/total amount of solute and solvent (in mol)

solubility of solids

increases as temperature increases

The bubbling that occurs when a can of soda is opened results from the...

reduced pressure of carbon dioxide over the liquid. At lower pressure, the carbon dioxide is less soluble and bubbles out of solution.

Miscible

-Describes two liquids that are soluble in each other -Like dissolves like -Nonpolar + Nonpolar -Polar + Polar

The lattice energy of NaCl is -787 kJ/mol and the enthalpy of hydration for NaCl is -783 kJ/mol. What is the enthalpy of solution of NaCl(s).

+4 kJ/ mol

A solution is prepared by dissolving 17.2 g of ethylene glycol (C2H6O2) in 0.500 kg of water. The final volume of the solution is 515 mL. For this solution, calculate: (a) molarity (b) molality (c) percent by mass(d) mole fraction (e) mole percent

(a) molarity: 0.538 M (b) molality: 0.5542 m (c) percent by mass: (17.2 g)/(17.2 g + 5.00 * 10^2 g) * 100 = 3.33 % (d) mole fraction: (0.2771)/(0.2771 + 27.75) (e) mole percent: 0.989%

Parts by mass

(mass solute/mass solution) * multiplication factor mass solution

Calculate the freezing point of a 2.6 m aqueous sucrose solution.

-4.836 degrees Celsius

Entropy

-A measure of disorder or randomness -measure of energy randomization or energy dispersal in a system.

Ideal gases mixing

-potential energy remains same even after they both combine -The pervasive tendency for all kinds of energy to spread out, or disperse, whenever it is not restrained from doing Ex: Neon and Argon mixing

dynamic equilibrium

-rates of dissolution and recrystallization become equal NaCl(s): --> H2O--->, <--- H20O<----- : ∆H2O Na+(aq) + Cl-(aq)

Tendency toward energy dispersal example

-transfer of thermal energy from hot to cold. If we heat one end of an iron rod, the thermal energy deposited at the end of the rod spontaneously spreads along the entire length of the rod.

The enthalpy of solution for cesium fluoride is -36.8kJ>mol. What can you conclude about the relative magnitudes of ∆Hsolute and ∆Hhydration?

-∆Hhydration>∆Hsolute, because the enthalpy of the solution is an exothermic process and bonds are being formed -When these solutes dissolve in water, the resulting solutions feel warm to the touch

∆Hsolute =

-∆Hlattice

A salt and a water solution remains liquid, even below...

0 degrees celsius

A solution contains 0.115 mol H2O and an unknown number of moles of sodium chloride. The vapor pressure of the solution at 30 °C is 25.7 torr. The vapor pressure of pure water at 30 °C is 31.8 torr. Calculate the number of moles of sodium chlo- ride in the solution.

0.01366 mol

A water sample contains the pollutant chlorobenzene with a concentration of 15 ppb (by mass). What volume of this water contains 5.00 * 10^2 mg of chlorobenzene? (Assume a density of 1.00 g/mL).

3.3 * 10^7 mL

What is the molarity of 6.55% by mass glucose solution? The density of the solution is 1.03 g/mL.

0.374 M

Calculate the boiling point of a 3.60 m aqueous sucrose solution.

1.8432 + 100 degrees celsius = 101.8432 degrees celsius

Calculate the freezing point of a 1.7 m aqueous ethylene glycol solution.

1.86 C/m * 1.7 m = 3.2 degrees celsius Change of temperature = 0-3.2= -3.2

The freezing point of an aqueous 0.050 m CaCl2 solution is -0.27 °C. What is the van't Hoff factor (i) for CaCl2 at this concentration? How does it compare to the predicted value of i?

2.9

Calculate the vapor pressure at 25 °C of a solution containing 99.5 g sucrose (C12H22O11) and 300.0 mL water. The vapor pressure of water at 25 °C is 23.8 torr. Assume the density of water is 1.00 g/mL.

23.39 Torr

The osmotic pressure of a solution containing 5.87 mg of an unknown protein per 10.0 mL of solution was 2.45 torr at 25 °C. Find the molar mass of the unknown protein.

4.45 * 103g>mol

What mass of sucrose (C12H22O11), in g, is contained in 355 mL (12 oz) of a soft drink that is 11.5% sucrose by mass? (Assume a density of 1.04 g>mL.)

42.458 grams

A solution contains 3.95 g of carbon disulfide (CS2) and 2.43 g of acetone (CH3COCH3). The vapor pressures at 35 °C of pure carbon disulfide and pure acetone are 515 torr and 332 torr, respectively. Assuming ideal behavior, calculate the vapor pressures of each of the components and the total vapor pressure above the solution.

433.2 Torr

How much ethylene glycol (C2H6O2), in grams, must be added to 1.0 kg of water to produce a solution that boils at 105.0 °C?

606.4 grams of ethylene glycol

Solution

A homogeneous mixture of two or more substances

Solvent

A liquid substance capable of dissolving other substances Majority component in solution Ex: Water

Solubility

A measure of how much solute can dissolve in a given solvent at a given temperature.

colligative property

A property of a solution that depends on the number, not the identity, of the solute particles.

A solution is saturated in both nitrogen gas and potassium bromide at 75 °C. When the solution is cooled to room temperature, what is most likely to occur? (a) Some nitrogen gas bubbles out of solution. (b) Some potassium bromide precipitates out of solution. (c) Some nitrogen gas bubbles out of solution, and some potassium bromide pre- cipitates out of solution. (d) Nothing happens.

B

Determine whether each compound is soluble in hexane. (a) water (H2O) (b) propane (CH3CH2CH3) (c) ammonia (NH3) (d) hydrogen chloride (HCl)

B

Which solution has the highest boiling point? (a) 0.50 M C12H22O11 (b) 0.50 M NaCl (c) 0.50 M MgCl2

C)The 0.50 M MgCl2 solution has the highest boiling point because it has the highest concentration of particles. We expect 1 mol of MgCl2 to form 3 mol of particles in solution (although it effectively forms slightly fewer).

Initially, table salt (NaCl) is a...

Crystal

spontaneous mixing example

Ex: Why sea water tends to attract itself when solutions with different solute concentrations come in contact, they spontaneously mix to result in a uniform distribution of solute throughout the solution

Common Non-polar Solvents

Hexane (C6H14) Diethyl ether (CH3CH2OCH2CH3) Toluene (C7H8) Carbon tetrachloride (CCl4)

The van't Hoff factors are not exactly equal to the expected values because some ions effectively pair in solution.

In other words, ideally we expect the dissociation of an ionic compound to be complete in solution. In reality, however, the dissociation is not complete— at any moment, some cations are effectively combined with the corresponding anions, slightly reducing the number of particles in solution.

Examples of miscibility

Intermolecular forces exist between each of the following: (a) the solvent and solute particles (b) the solvent particles themselves (c) the solute particles themselves

What interactions happens when Water and NaCl combine?

Ion-Dipole interactions

Suppose a water sample at 25 °C contains 0.90 mol of water and 0.10 mol of a nonvolatile solute such as sucrose. The pure water would have a vapor pressure of 23.8 torr. Calculate the vapor pressure of the solution.

Psolution = xH2OP°H2O= 0.90(23.8 torr) = 21.4 torr

Raoult's Law equation

Psolution = xsolventP°solvent Vapor pressure of the solution = mole fraction of the solvent * vapor pressure of the pure solute at same temperature

Henry's Law equation

Sgas = kHPgas S1/P1 = S2/P2

Determine the solubility of oxygen in water at 25 °C exposed to air at 1.0 atm. Assume a partial pressure for oxygen of 0.21 atm.

Solubility of gas = 2.73 * 10^-4

Solution A is a 1.0 M solution with a nonionic solute and water as the solvent. Solution B is a 1.0 M solution with the same nonionic solute and ethanol as the solvent. Which solution has the greater change in its boiling point (relative to the pure solvent)?

Solution B, ethanol

Crystallization

The process by which atoms are arranged to form a material with a crystal structure

Recrystallization

The process by which bonds between atoms in minerals break and re-form in new ways -Over time, however, the concentration of dissolved sodium chloride in the solution increases. This dissolved sodium chloride can then begin to recrystallize as solid sodium chloride -At first, the rate of dissolution far exceeds the rate of recrystallization. But as the concentration of dissolved sodium chloride increases, the rate of recrystallization also increases.

When a solute is added to a pure solvent...

The rate of condensation increases than the rate of vaporization...

ambient temperature

The temperature of the surrounding environment.

Common Polar Solvents

Water (H2O) Acetone (CH3COCH3) Methanol (CH3OH) Ethanol (CH3CH2OH)

Solubility

[Henry's Constant] * [Partial Pressure]

semipermeable membrane

a membrane that selectively allows some sub- stances to pass through but not others

aqueous solution

a solution in which water is the solvent

saturated solution

a solution that cannot dissolve any more solute under the given conditions -even if more solute was added, it will not dissolve

ideal solution

a solution that obeys Raoult's law Ptot =PA +PB

concentrated solution

contains large quantities of solute relative to the amount of solvent

supersaturated solution

contains more dissolved solute than a saturated solution at the same temperature

dilute solution

contains small quantities of solute relative to the amount of solvent

solubility of gases

decreases as temperature increases Ex: When water is boiling, before water reaches its boiling point, you will see small bubbles develop in the water which are dissolved air (mostly nitrogen and oxygen) coming out of solution. (Once the water boils, the bubbling becomes more vigorous— these larger bubbles are composed of water vapor.) The dissolved air comes out of solution because—unlike solids,

Osmosis

flow of solvent from a solution of lower solute concentration to one of higher solute concentration

van't Hoff(i) factor equation

i = (moles of particles in solution)/(moles of formula units dissolved)

Molality

mol solute/kg solvent

Molarity

moles of solute/liters of solution

Parts per million by mass (ppm)

multiplication factor = 10^6

Parts per billion by mass (ppb)

multiplication factor = 10^9

Concentrated solutions draw solvent from more dilute solutions because of..

nature's tendency to mix

The dissolution of a solute in a solvent is an equilibrium process similar to the equilibrium process associated with a...

state change

spontaneous mixing

substances tend to combine into uniform mixtures rather than sepa- rating into pure substances

boiling point elevation

the difference in temperature between the boiling point of a solution and the boiling point of the pure solvent

freezing point depression

the difference in temperature between the freezing point of a solution and the freezing point of the pure solvent

lattice energy

the energy required to separate 1 mol of the ions of an ionic compound

heat of hydration

the enthalpy change that occurs when 1 mol of the gaseous solute ions is dissolved in water

Higher the pressure of a gas above a liquid..

the more soluble the gas is in the liquid

van't Hoff factor(i)

the ratio of moles of particles in solution to moles of solute dissolved

Henry's Law

the solubility of a gas in a liquid is directly proportional to the partial pressure of that gas on the surface of the liquid

Raoult's Law

the vapor pressure of a solution is directly proportional to the mole fraction of solvent present

Parts by volume (%, ppm, ppb)

volume solute/volume solution x multiplication factor

Calculate the freezing point of an aqueous 0.10 m FeCl3 solution using a van't Hoff factor of 3.2.

Δ T = 0.5952

Enthalpy of solution (∆Hsoln) equation

ΔHsoln = ΔHsolute endothermic (positive) + ΔHhydration exothermic (negative)

osmotic pressure (Π), is given by the equation:

Π = MRT M= Molarity T= Temperature in K R= Ideal gas constant 0.08206 L Π = In ATM (divide by 760)

NaCl(s) --->(H2O)----> Na + (aq) + Cl - (aq)

∆Hsoln = +3.88 kJ/mol

Enthalpy of solution (∆Hsoln) equation

∆Hsoln = ∆Hsolute + ∆Hsolvent + ∆Hmix endothermic (+) endothermic (+) exothermic (-)

The amount that the boiling point is raised for solutions is given by the equation:

∆Tb = m * Kb For water, Kb = 0.512°C/m

Three equations for colligative properties

∆Tf = im * Kf (freezing point depression) ∆Tb = im * Kb (boiling point elevation) Π = iMRT (osmotic pressure)

Amount that the freezing point is lowered for solutions equation:

∆Tf = m * Kf m is the molality For water, Kf = 1.86°C/m