Solubility Rules Mcat

b) Ideal gas law derivatives

MCAT Physical : Solubility Rules

Which of the following reactions will produce a precipitate?

Knowledge of basic solubility rules is enough to answer this question. Nitrates and salts of alkali metals are always soluble, as are salts of ammonium. Acetates are also always soluble. Acid-base reactions, such as with hydrofluoric acid, produce a soluble salt and water. Sulfates are commonly soluble, with certain exceptions (mostly alkaline earth metals).

The only reaction that produces an insoluble product is that between silver nitrate and potassium chloride. Silver chloride is a common precipitate obtained in double replacement reactions.

Example Question #2 : Solubility Rules

Boiling point is the temperature a liquid needs to achieve in order to begin its transformation into a gaseous state. Campers and hikers who prepare food during their trips have to account for differences in atmospheric pressure as they ascend in elevation. During the ascent, the decrease in atmospheric pressure changes the temperature at which water boils.

Further complicating the matter is the observation that addition of a solute to a pure liquid also changes the boiling point. Raoult’s Law can be used to understand the changes in boiling point if a non-volatile solute is present, as expressed here.

In this law, is the mole fraction of the solvent, is the vapor pressure of the pure solvent, and is the vapor pressure of the solution. When this vapor pressure is equal to the local atmospheric pressure, the solution boils.

A scientist is studying boiling point changes with the addition of solutes, and creates a colloid. A colloid is similar to a solution because both will possess which of the following characteristics?

I. They both show the Tyndall effect on light

II. They both involve the suspension of only molecular-sized particles

III. They both involve the suspension of particles that are too small to be individually distinguished with the naked eye

A colloid is a suspension of particles larger than molecules, but too small to be individually distinguished by the naked eye. Only colloids disperse light by the Tyndall effect. Milk is an example of a colloid.

Example Question #3 : Solubility Rules

Which of the following compounds would be generally insoluble in an aqueous solution?

Knowing some of the general solubility trends will greatly facilitate your understanding of solubility in chemistry. Here are a couple guidelines you can follow in order to predict which compounds are soluble.

1. Compounds containing alkali metals, ammonium cations, or nitrate anions are soluble.

2. Compounds containing halogen anions are soluble. Key exceptions are halogens attached to silver, mercury, and lead.

3. Sulfates are soluble, except when attached to heavier alkaline metals, like barium (thus the correct answer).

4. Carbonates, phosphates, and hydroxides are generally insoluble; however, if they are attached to one of the ions mentioned in one of the above points, they are soluble.

Example Question #4 : Solubility Rules

Which of the following molecules is insoluble?

These solubility rules should be known for the MCAT and are presented as a hierarchy.

1. All group 1 salts and ammonium salts are soluble

2. All nitrates, perchlorates, and acetates are soluble

3. All mercury, lead, and silver salts are NOT soluble

Understanding these solubility rules as a hierarchy, we can understand why Mg(NO₃)₂ and AgNO₃ are soluble and why AgCl is not soluble.

Example Question #5 : Solubility Rules

Which compound is most likely to be soluble in pentane?

Molecules are most soluble in solvents that possess similar properties and intermolecular forces to the solute.

Pentane is a non-polar compound, which interacts predominately through london dispersion forces. Ammonia, silver chloride, and phosphorus trichloride are all polar molecules. Ammonia has a lone pair on the nitrogen; silver is an ionic compound; phosphorus trichloride has lone pairs on both the phosphorus and chlorine atoms.

In contrast, carbon dioxide has lone pairs only on the oxygen atoms and has a linear geometry. This creates a line of symmetry in the molecule such that the net polarities of the carbon-oxygen bonds cancel each other. Even though carbon dioxide has polar bonds, it is not a polar molecule and would likely dissolve in pentane.

Example Question #6 : Solubility Rules

All of the following compounds are soluble in water except __________ .

Compounds that contain sulfate groups ( )are soluble in water, unless they are bound to mercury, strontium, lead, calcium, or barium. Hence, barium sulfate, , is insoluble in water.

Compounds that contain nitrates ( ), ammonium ( ), and alkali metals are generally soluble in water. Compounds containing halogens are soluble in water unless they are bound to mercury, lead, or silver.

Example Question #7 : Solubility Rules

Which salt will produce a basic solution when dissolved in water?

When is dissolved in water, it forms and . Both of these are basic compounds.

Each of the other answer options will result in at least one acidic compound when dissolved in solution.

Example Question #8 : Solubility Rules

Substances for which pure water would not be an efficient solvent are __________ .

those that have large dipole moments

those with evenly dispersed electrons

those that have high charge densities

those that tend to form hydrogen bonds

those with evenly dispersed electrons

Since water is polar, it dissolves substances that have electrostatic charge due to electron arrangement. All of the answer choices describe molecules that would have positive and negative components except those with evenly dispersed electrons. This describes a nonpolar molecule, which would not dissolve in water.

Emory University, Bachelor of Science, Health and Wellness, General.

University of Pittsburgh-Pittsburgh Campus, Bachelors, Neuroscience.

All MCAT Physical Resources

Report an issue with this question

If you’ve found an issue with this question, please let us know. With the help of the community we can continue to improve our educational resources.

DMCA Complaint

If you believe that content available by means of the Website (as defined in our Terms of Service) infringes one or more of your copyrights, please notify us by providing a written notice (“Infringement Notice”) containing the information described below to the designated agent listed below. If Varsity Tutors takes action in response to an Infringement Notice, it will make a good faith attempt to contact the party that made such content available by means of the most recent email address, if any, provided by such party to Varsity Tutors.

Your Infringement Notice may be forwarded to the party that made the content available or to third parties such as ChillingEffects.org.

Please be advised that you will be liable for damages (including costs and attorneys’ fees) if you materially misrepresent that a product or activity is infringing your copyrights. Thus, if you are not sure content located on or linked-to by the Website infringes your copyright, you should consider first contacting an attorney.

Please follow these steps to file a notice:

You must include the following:

A physical or electronic signature of the copyright owner or a person authorized to act on their behalf; An identification of the copyright claimed to have been infringed; A description of the nature and exact location of the content that you claim to infringe your copyright, in \ sufficient detail to permit Varsity Tutors to find and positively identify that content; for example we require a link to the specific question (not just the name of the question) that contains the content and a description of which specific portion of the question – an image, a link, the text, etc – your complaint refers to; Your name, address, telephone number and email address; and A statement by you: (a) that you believe in good faith that the use of the content that you claim to infringe your copyright is not authorized by law, or by the copyright owner or such owner’s agent; (b) that all of the information contained in your Infringement Notice is accurate, and (c) under penalty of perjury, that you are either the copyright owner or a person authorized to act on their behalf.

Send your complaint to our designated agent at:

Charles Cohn Varsity Tutors LLC
101 S. Hanley Rd, Suite 300
St. Louis, MO 63105

Or fill out the form below:

Solutions and Gases for the MCAT: Everything You Need to Know

Learn key MCAT concepts about solutions and gases, plus practice questions and answers

(Note: This guide is part of our MCAT General Chemistry series.)

Table of Contents

Part 1: Introduction to solutions and gases

Part 2: Solubility of ions

a) Solubility rules

b) Concentration units

c) Colligative properties

Part 3: Solubility of reactions

a) Common ion effect

b) Solubility equilibria

Part 4: Gas law equations

a) Ideal gas law

b) Ideal gas law derivatives

c) Partial pressure

Part 5: High-yield terms

Part 6: Passage-based questions and answers

Part 7: Standalone questions and answers

Part 1: Introduction to solutions and gases

What happens as you stir sugar into a cup of coffee or salt in water? Perhaps predictably, the solid sugar or salt dissolves into its components: charged ions that are invisible to the naked eye. As ions become dissolved, they can change the chemistry of the aqueous solution they are in. Of course, this has special implications for compounds in biological systems, including acids and bases.

In this guide, we will cover everything you need to know about solutions and gases for the MCAT. You’ll run into some familiar variables, such as the equilibrium constant. However, this time it’ll be in the context of dissociation reactions. As you read through this article, challenge yourself to connect the topics discussed here with topics you’ve encountered during your MCAT prep.

Throughout this guide, there are several important terms and concepts marked in bold. At the end of the guide, there is also a practice passage and a set of questions for you to test your knowledge against.

Part 2: Solubility of ions

a) Solubility rules

Solubility refers to the ability of a solute to dissolve in a particular solvent. For example, vitamins A, D, E, and K are considered fat-soluble vitamins because they dissolve in fat and are stored in adipose tissue. When the solute is in an equilibrium between its dissolved and undissolved state, the solution is considered to be saturated. Any additional solute added will be insoluble and form a precipitate, the solute’s undissolved solid form. These are referred to as precipitation reactions.

The solvent used and the temperature of a solution can impact the solubility of a substance. For instance, polar solvents (such as water) tend to dissolve other polar or ionic compounds. Nonpolar solvents (such as oil or fat) tend to dissolve other nonpolar compounds (such as vitamin A).
In the context of the MCAT, water is the most commonly seen solvent. The table below summarizes several solubility rules you should be familiar with for test day. Note that there are several exceptions to each of these solubility rules.

Water Solubility Rules
Salts containing Group I elements (alkali metals) are soluble
Salts with the ammonium ion (NH 4+ ) are soluble
Salts with the acetate ion (CH3COO – ) are soluble
Salts with the nitrate ion (NO3 – ) are soluble
Salts containing the sulfate ion (SO4 2- ) are soluble Exceptions: SrSO4, PbSO4, BaSO4, Ag2SO4, CaSO4
Sulfites (SO3 2- ) are insoluble Exceptions: Sulfites with Group I elements and ammonium
Sulfides (S 2- ) are insoluble Exceptions: Sulfides with Group I elements and ammonium
Halides are soluble (e.g., Iodine, Chlorine, Bromine) Exceptions: Fluoride and halides containing Pb 2+ , Ag + , and (Hg2) 2+
Hydroxide salts with ammonium, Group I elements (alkali metals), and certain Group II elements (Ca 2+ , Sr 2+ , and Ba 2+ ) are soluble All other hydroxide salts are insoluble
Phosphates (PO4 3- ) are insoluble Exceptions: Phosphates containing Group I elements and ammonium
Carbonates (CO3 2- ) are insoluble (e.g., CaCO3, FeCO3, and SrCO3) Exceptions: Carbonates containing Group I elements and ammonium