14. Solutions

Solutions: Solubility and Intermolecular Forces

Dissolution of NaCl in water

INSTRUCTOR: When an ionic substance, such as sodium chloride, is placed in water, water molecules interact with the ions on the surface. If the salt is soluble, the attractive interactions with water molecules overcome the ionic attractions within the lattice. The solvated ions move off the surface and become separated in solution. Notice that water molecules cluster about the anions with the hydrogens directed toward the negatively charged ion. On the other hand, water molecules interact with the positively charged cations through the lone pairs of electrons on the oxygens.

Classify the strongest type of intermolecular force in the follow- ing interactions: solvent–solvent, solvent–solute, and solute– solute when solid iodine 1I22 is placed in the water. Based on these interactions, predict whether I2 is soluble in water.

Temperature also affects the solubility of solids.

Gas bubbles out of the solution and solid dissolves.

Correct, temperature, in general, affects the solubility of solids and gases in an opposite manner.

Temperature also affects the solubility of gases.

Gas bubbles out of the solution and solid precipitates.

Recall that the effect of temperature in general is not the same for gases and solids.

 Recall that, generally, temperature affects the solubility of gases and solid differently. 

Consider a solution that is saturated with a gas and a solid at room temperature.   Which of the following will occur when the solution is heated by 50&#176;C?

When lithium iodide (LiI) is dissolved in water, the solution becomes hotter.
c. Sketch a qualitative energy diagram similar to Figure 13.7 for the dissolution of LiI.

In which solvent does sodium acetate 1CH COONa2 have the highest solubility (a) Acetone CH3OCH3 (b) Methanol (CH3OH) (c) Ethanol (CH3CH2OH) (d) Pentane (CH3CH2CH2CH2CH3)

Solute, Solvent, & Solution -  Solubility Chemistry

Which diagram best represents a liquid–liquid emulsion
such as milk? The colored balls represent different liquid
molecules. [Section 13.6]
<img src="https://lightcat-files.s3.amazonaws.com/problem_images/c7422867ef77d18c-1666017645006.jpg" alt="" />

Water does not easily remove grease from dishes or hands because
grease is nonpolar and water is polar. The addition of soap
to water, however, allows the grease to dissolve. Study the structure
of sodium stearate (a soap) and describe how it works.
<img src="https://lightcat-files.s3.amazonaws.com/problem_images/361157b225d1708c-1660246805877.jpg" alt="" />

Indicate the most important type of intermolecular attraction responsible for solvation in the following solution:Methanol, CH3OH, dissolved in ethanol, CH3CH2OH

Solubility and the Born-Haber Cycle

KBr is relatively soluble in water, yet its enthalpy of solution
is + 19.8 kJ/mol. Which of the following statements provides the best explanation for this behavior?
(a) Potassium salts are always soluble in water.
(b) The entropy of mixing must be unfavorable.
(c) The enthalpy of mixing must be small compared to the
enthalpies for breaking up water–water interactions and
K–Br ionic interactions.
(d) KBr has a high molar mass compared to other salts like
NaCl.

Factors affecting solubility

When ammonium chloride dissolves in water, the solution
becomes colder. (a) Is the solution process exothermic or
endothermic?

Recall, Solubility is a chemical property that deals with ability of a solute to dissolve in a solvent.

Water is a good solvent for many substances. What is the
molecular basis for this property, and why is it significant?

Ion Dipole Forces & Ion Induced Dipole Interactions - Chemistry

Solubility

For each compound, would you expect greater solubility in water or in hexane? Indicate the kinds of intermolecular forces that occur between the solute and the solvent in which the molecule is most soluble.
a. glucose

How does a Solute Dissolve in a Solvent? | Solutions | Chemistry | Don't Memorise

Indicate whether each statement is true or false:
(c) The solubility of most gases in water decreases as the
temperature increases because water is breaking its hydrogen bonding to the gas molecules as the temperature is raised.

Solutions: Solubility and Intermolecular Forces Example 2

Indicate the principal type of solute–solvent interaction
in each of the following solutions and rank the solutions
from weakest to strongest solute–solvent interaction: (b) CH2Cl2 in benzene 1C6H62

When lithium iodide (LiI) is dissolved in water, the solution becomes hotter.
a. Is the dissolution of lithium iodide endothermic or exothermic?

Indicate the type of solute–solvent interaction (Section 11.2)
that should be most important in each of the following solutions:
(c) KBr in water

When ammonium chloride dissolves in water, the solution 
becomes colder. (b) Why does the solution form?

Determine whether each pair of compounds forms a 
homogeneous solution when combined. For those that form 
homogeneous solutions, indicate the type of forces that are 
involved. 
d. CH3CH2OH and H2O

Which would you expect to have the larger hydration 
energy, SO42- or ClO4-? Explain.

Determine whether each pair of compounds forms a
homogeneous solution when combined. For those that form
homogeneous solutions, indicate the type of forces that are
involved.
a. CCl4 and H2O

Two nonpolar organic liquids, hexane 1C6H142 and heptane
1C7H162, are mixed. (a) Do you expect ∆Hsoln to be a large
positive number, a large negative number, or close to zero?
Explain.

The solubility of carbon tetrachloride (CCl4) in water at 25 °C is 
1.2 g>L. The solubility of chloroform (CHCl3) at the same temperature 
is 10.1 g>L. Why is chloroform almost ten times more 
soluble in water than carbon tetrachloride?

In the Theory of Likes Dissolve Likes the solvent can only completely dissolve the solute if they share same Intermolecular Forces and/or Polarity.&nbsp;

Indicate the type of solute–solvent interaction (Section 11.2)
that should be most important in each of the following solutions:
(b) methanol 
1CH3OH2 in water

Compounds like sodium stearate, called “surfactants” in
general, can form structures known as micelles in water,
once the solution concentration reaches the value known
as the critical micelle concentration (cmc). Micelles contain dozens to hundreds of molecules. The cmc depends
on the substance, the solvent, and the temperature.

(a) The turbidity (the amount of light scattering) of solutions increases dramatically at the cmc. Suggest an explanation. .

Solutions: Solubility and Intermolecular Forces Concept 2

Which of the following in each pair is likely to be more soluble in water: (a) cyclohexane 1C6H122 or glucose 1C6H12O62,

Two nonpolar organic liquids, hexane 1C6H142 and heptane
1C7H162, are mixed. (b) Hexane and heptane are miscible with each
other in all proportions. In making a solution of them, is
the entropy of the system increased, decreased, or close to
zero, compared to the separate pure liquids?

Solutions: Solubility and Intermolecular Forces Example 1

Aerosols are important components of the atmosphere. 
Does the presence of aerosols in the atmosphere increase or 
decrease the amount of sunlight that arrives at the Earth’s 
surface, compared to an “aerosol-free” atmosphere? Explain your reasoning.

Water & Solutions - for Dirty Laundry: Crash Course Chemistry #7

Depending on the solute and solvent, this enthalpy can be either exothermic or endothermic.

Correct; as the solute and solvent particles form attractions for each other, energy is released.

Energy is required to separate the solute particles.

Energy is required to separate the solvent particles.

None of the enthalpies is always exothermic.

One of the enthalpies always involves the formation of new attractions.

 Recall that energy is required to overcome the forces attracting one particle to another. 

According to Hess’s law which of the following terms for the formation of a solution is always exothermic?

Which of the following in each pair is likely to be more soluble in water:
(c) HCl or ethyl chloride 1CH3CH2Cl2?
Explain in each case.

Factors Affecting Solubility

For each compound, would you expect greater solubility in water or in hexane? Indicate the kinds of intermolecular forces that would occur between the solute and the solvent in which the molecule is most soluble.
d. ethylene glycol

Intermolecular Forces

The formation of the solution causes an increase in energy.

One substance is polar and the other is nonpolar.

The formation of the solution causes an increase in randomness.

Strong intermolecular attraction between the solute molecules.

Two pure chemical substance are likely to mix and form a solution if:

An ionic compound has a very negative ∆Hsoln in water
(b) Which term would you expect to be the 
largest negative number: ∆Hsolvent, ∆Hsolute, or ∆Hmix

Indicate the principal type of solute–solvent interaction
in each of the following solutions and rank the solutions
from weakest to strongest solute–solvent interaction: (a) KCl in water

When lithium iodide (LiI) is dissolved in water, the solution becomes hotter.
b. What can you conclude about the relative magnitudes of the lattice energy of lithium iodide and its heat of hydration?

Predict whether the solubility of butane, C4H10, is greater in water or benzene, C6H6.

Indicate the principal type of solute–solvent interaction
in each of the following solutions and rank the solutions
from weakest to strongest solute–solvent interaction: (c) methanol 1CH3OH2 in water

This figure shows the interaction of a cation with surrounding water molecules. 

(b) Which of the following explanations accounts for the
fact that the ion–solvent interaction is greater for Li+
than for K+?
a. Li+ is of lower mass than K+.
b. The ionization energy of Li is higher than that for K.
c. Li+ has a smaller ionic radius than K+.
d. Li has a lower density than K.
e. Li reacts with water more slowly than K. [Section 13.1]

hexane (CH3 CH2 CH2 CH2 CH2 CH3)

Hexane is nonpolar while aspirin has polar groups.

acetone (CH3CO CH3)

Correct, the polarity of acetone is the closest to that of aspirin.

toluene (C6 H5 CH3)

Toluene is nonpolar while aspirin has polar groups.

Any of the above would be a good solvent for aspirin.

All of these solvents are not of the same polarity.

None of the above would be a good solvent for aspirin.

One of the solvents is very similar to aspirin in polarity.

&#8216;Like dissolves like&#8217; &#8211; A polar solvent will dissolve a polar molecule; a nonpolar solvent will dissolve a nonpolar molecule.

Which of the following solvents would you expect to dissolve aspirin? <img src="https://media.pearsoncmg.com/ph/esm/esm_tro_chemistry_6/msa/content/practice-quiz/img/aspirin.jpg" alt=" Structural formula for aspirin showing a six-membered carbon ring with alternating single and double bonds with a carboxylic acid group (C doubly bonded to an oxygen and to an OH group) bonded to one of the carbon atoms and an ester group (C doubly bonded to an oxygen atom and to an oxygen atom which is in turn bonded to a CH3 group) bonded to an adjacent carbon atom.">

HOCH2CH2CH2OH

CH3CH2CH2CH3

CH3CH2CH2OH

Which of the following solutes will most readily dissolve in H2O?

Which of the following in each pair is likely to be more
soluble in hexane, C6H14:(b) benzene 
1C6H62 or glycerol, CH21OH2CH1OH2CH2OH,

Indicate the type of solute–solvent interaction (Section 11.2)
that should be most important in each of the following solutions: (a) CCl4 in benzene

Indicate the type of solute–solvent interaction (Section 11.2)
that should be most important in each of the following solutions:
(d) HCl in acetonitrile 
1CH3CN2

If a single 5-g block of NaCl is placed in water, it dissolves slowly, but if 5 g of powdered NaCl is placed in water, it dis- solves rapidly. Explain.

Which molecule would you expect to be more soluble in water: 
CH3CH2CH2OH or HOCH2CH2CH2OH?

When lithium iodide (LiI) is dissolved in water, the solution becomes hotter.
d. Why does the solution form? What drives the process?

Two nonpolar organic liquids, hexane 1C6H142 and heptane
1C7H162, are mixed (b) Hexane and heptane are miscible with each 
other in all proportions. In making a solution of them, is 
the entropy of the system increased, decreased, or close to 
zero, compared to the separate pure liquids?

A supersaturated solution of sucrose (C12H22O11) is made by
dissolving sucrose in hot water and slowly letting the solution cool to room temperature. After a long time, the excess
sucrose crystallizes out of the solution. Indicate whether
each of the following statements is true or false:
(b) After the excess sucrose has crystallized out, the system
is now unstable and is not in equilibrium.

When do two substances form a solution (part 1) | Solutions | Chemistry | Don't Memorise

Reactions in Aqueous Solution

Which of the following statements is/are true?I. The hydrocarbon methane (CH4) will dissolve completely in acetone (CH3COCH3).II. Ammonia (NH3) will form a heterogeneous mixture with carbon tetrachloride (CCl4).III. Pentane (C5H12) will form a homogeneous mixture with carbon tetrabromide (CBr4).IV. Methanethiol (CH3SH) is miscible in fluoromethane (CH3F).

Arrange the following compounds in order of their expected increasing solubility in water: Br2, KBr, toluene (C7H8, a constituent of gasoline).

Oil and water are immiscible. Which is the most likely
reason? 
(a) Oil molecules are denser than water. 
(b) Oil molecules are composed mostly of carbon and hydrogen.
(c) Oil molecules have higher molar masses than water.
(d) Oil molecules have higher vapor pressures than water.
(e) Oil molecules have higher boiling points than water.

Entropy of the universe is always increasing.

A solid forming from a dissolved solute results in a decrease in disorder.

Dissolving a salt in water to make an aqueous solution results in an increase in entropy.

Entropy explains why two ideal gases have a natural tendency to mix.

Solids have less entropy than do liquids.

Recrystallization is a process that shows an increase in entropy.

Correct, the formation of the solid from the dissolved solute decreases entropy.

 Review the effects of entropy on the formation of solutions. 

Which of the following is false about entropy?

The “free-base” form of cocaine (C17H21NO4) and its protonated hydrochloride form (C17H22ClNO4) are shown
below; the free-base form can be converted to the hydrochloride form with one equivalent of HCl. For clarity, not
all the carbon and hydrogen atoms are shown; each vertex
represents a carbon atom with the appropriate number of
hydrogen atoms so that each carbon makes four bonds to
other atoms
<img src="https://lightcat-files.s3.amazonaws.com/problem_images/d26a8332cb3715bd-1666021370949.jpg" alt="" />
(a) One of these forms of cocaine is relatively water-soluble:
which form, the free base or the hydrochloride?

Look at the solubility graph in Figure 13.7, and estimate which member of each of the following pairs has the higher molar solubility at the given temperature.
(b) CH3CO2Na or glucose at 20 °C<img src="https://lightcat-files.s3.amazonaws.com/problem_images/72a6978eab26317d-1671655368747.jpg" alt="" />

Consider two ionic solids, both composed of singly charged 
ions, that have different lattice energies.
(b) If not, which solid
will be more soluble in water, the one with the larger lattice
energy or the one with the smaller lattice energy? Assume
that solute–solvent interactions are the same for both solids. [Section 13.1]

A series of anions is shown below:
<img src="https://lightcat-files.s3.amazonaws.com/problem_images/a3ad7b189b3bf7d3-1666023278003.jpg" alt="" />
The anion on the far right is called “BARF” by chemists, as
its common abbreviation sounds similar to this word.
(d) Tetrabutylammonium, (CH3CH2CH2CH2)4N + is a 
bulky cation. Which anion, when paired with the 
tetrabutylammonium cation, would lead to a salt 
that will be most soluble in nonpolar solvents?

When lithium chloride dissolves in water, the temperature of the solution increases. Which diagram represents the enthalpy changes of the steps in the solution-making process? (LO 13.2)

Pick an appropriate solvent from Table 13.3 to dissolve each substance. State the kind of intermolecular forces that would occur between the solute and solvent in each case. 
b. sodium chloride (ionic)

Solutions: Solubility and Intermolecular Forces Concept 1

There are three types of interactions involved.

Correct, the formation of a solution depends on all three types of intermolecular forces.

Solute-solute interactions must be overcome for the solution to form.

 Review the formation of a solution from the separated solvent and solute. 

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Professor Dave Explains

1. Intro to General Chemistry

2. Atoms & Elements

3. Chemical Reactions

4. BONUS: Lab Techniques and Procedures

5. BONUS: Mathematical Operations and Functions

6. Chemical Quantities & Aqueous Reactions

7. Gases

8. Thermochemistry

9. Quantum Mechanics

10. Periodic Properties of the Elements

11. Bonding & Molecular Structure

12. Molecular Shapes & Valence Bond Theory

13. Liquids, Solids & Intermolecular Forces

15. Chemical Kinetics

16. Chemical Equilibrium

17. Acid and Base Equilibrium

18. Aqueous Equilibrium

19. Chemical Thermodynamics

20. Electrochemistry

21. Nuclear Chemistry

22. Organic Chemistry

23. Chemistry of the Nonmetals

24. Transition Metals and Coordination Compounds

[BOOK CHEM] Clutch Version

Types of Aqueous Solutions

When an ionic solid dissolves, ions leave the solid and become dispersed in the solvent. Three possible aqueous solutions can be formed:saturated, unsaturated and supersaturated.

Boiling Point Elevation

Boiling Point Elevation is the phenomenon when adding a solute to a pure solvent results in increased boiling point of the solvent.

Intro to Henry's Law

According to&nbsp;Henry's Law, at a constant temperature the amount of a gas dissolved in a solvent is directly proportional to its partial pressure when it is in equilibrium with its liquid phase.&nbsp;

Osmotic Pressure

Osmotic Pressure is the force that drives Osmosis from higher concentration to lower concentration.

Mole Fraction

Mole Fraction (X) relates the moles of solute and solvent within a solution.&nbsp;

The Colligative Properties

The&nbsp;Colligative Properties&nbsp;explain what happens to a pure solvent as it transitions to a solution.

Molality

Molality (m)&nbsp;represents the number of moles of solute dissolved per kilogram of solvent.&nbsp;

Freezing Point Depression

Freezing Point Depression is the phenomenon when adding a solute to a pure solvent results in decreased freezing point of the solvent.

Solutions are homogeneous mixtures that result from the dissolving of a solute by a solvent.

Vapor Pressure Lowering (Raoult's Law)

Vapor Pressure is the pressure exerted by a gas at equilibrium with its liquid phase at a specific temperature in a closed system.

Henry's Law Calculations

To calculate solubility of a dissolves gas, Henry's Law Constant and partial pressure are used.

Solutions: Mass Percent

Mass Percent represents grams of solute per grams of solution, multiplied by 100.

Osmosis

Osmosis is the net movement of solvent across a semipermeable membrane.

Parts per Million (ppm)

<div dir="auto"><div contenteditable="true"dir="auto"spellcheck="true">Parts per Million (ppm) and Parts per Billion (ppb) are used to express extremely dilute solution concentrations.</div></div>