The undissolved pure solid does not appear in the solubility product expression for a slightly soluble salt.
Correct Answer
True
True. A pure solid has a constant activity, so it is left out of the equilibrium expression, and Ksp includes only the dissolved ion concentrations raised to their coefficients.
Category: Solubility Product
Question 2
Adding more undissolved solid to a saturated solution of a slightly soluble salt raises the concentration of its dissolved ions.
Correct Answer
False
False. A saturated solution already holds the equilibrium concentration of ions at that temperature, and extra solid does not change it because the solid does not appear in the Ksp expression. The ion concentrations stay the same.
Category: Solubility Product
Question 3
In a saturated solution prepared by dissolving only Mg(OH)2 in pure water, the hydroxide ion concentration is twice the magnesium ion concentration.
Correct Answer
True
True. Each formula unit of Mg(OH)2 releases one Mg2+ and two OH- ions, so when the salt is the only source of these ions, [OH-] = 2[Mg2+]. This ratio is what makes Ksp equal to 4s^3 for this salt.
Category: Molar Solubility
Question 4
The Ksp of a slightly soluble salt changes when a soluble compound containing a common ion is added to the solution.
Correct Answer
False
False. Ksp is constant at a given temperature. Adding a common ion shifts the equilibrium and lowers the salt's solubility, but the product of the ion concentrations returns to the same Ksp value.
Category: Common Ion Effect
Question 5
Calculating molar solubility directly from Ksp gives a reliable result only when the dissolved ions undergo no significant further reactions, such as with water or ligands.
Correct Answer
True
True. The simple relationship between Ksp and solubility assumes the solid only dissociates into its ions. If an ion also reacts, for example by acting as a base or forming a complex, the actual solubility is larger than the simple calculation predicts.
Category: Molar Solubility
Question 6
Adding lead(II) nitrate to a saturated solution of lead(II) iodide causes some lead(II) iodide to precipitate.
Correct Answer
True
True. Lead(II) nitrate supplies Pb2+, an ion shared with PbI2. The added common ion makes the ion product exceed Ksp, so the equilibrium shifts toward the solid and some PbI2 comes out of solution.
Category: Common Ion Effect
Question 7
A Lewis base is a species that accepts an electron pair to form a coordinate covalent bond.
Correct Answer
False
False. A Lewis base donates an electron pair. The species that accepts the electron pair is the Lewis acid.
Category: Lewis Acids and Bases
Question 8
Every Brønsted-Lowry acid-base reaction can also be described as a Lewis acid-base reaction in which H+ is the electron-pair acceptor.
Correct Answer
True
True. When a base accepts a proton, it does so by donating a lone pair to H+, so H+ acts as a Lewis acid. Brønsted-Lowry reactions are therefore one subset of the broader Lewis acid-base model.
Category: Lewis Acids and Bases
Question 9
A very large formation constant for a complex ion means that most of the free metal ion remains uncomplexed at equilibrium.
Correct Answer
False
False. A large Kf means the formation reaction lies far toward the complex, so nearly all of the metal ion is bound by ligands and very little free metal ion remains.
Category: Complex Ions
Question 10
Boron trifluoride reacts with fluoride ion to form BF4-, with the fluoride ion donating an electron pair to boron.
Correct Answer
True
True. The fluoride ion acts as a Lewis base by donating a lone pair, and the electron-deficient boron of BF3 acts as a Lewis acid. The product, BF4-, is a Lewis acid-base adduct.
Category: Lewis Acids and Bases
Question 11
Water cannot act as a ligand in a complex ion because it is a neutral molecule.
Correct Answer
False
False. A ligand needs a lone pair to donate, not a charge. Neutral molecules such as H2O and NH3 are common ligands, bonding to metal ions through lone pairs on oxygen and nitrogen.
Category: Complex Ions
Question 12
Rising levels of dissolved carbon dioxide make seawater more acidic, which increases the tendency of the calcium carbonate in coral to dissolve.
Correct Answer
True
True. Dissolved CO2 forms carbonic acid, and the added H+ converts carbonate ions to hydrogen carbonate. Removing carbonate shifts the calcium carbonate dissolution equilibrium toward dissolved ions, which threatens coral reefs.
Category: Coupled Equilibria
Question 13
Fluorapatite in tooth enamel dissolves in acid more readily than hydroxyapatite does.
Correct Answer
False
False. Fluoride is a much weaker base than hydroxide, so fluorapatite reacts less with acid and resists dissolving better. That is why fluoride in toothpaste and drinking water helps protect enamel.
Category: Coupled Equilibria
Question 14
Mercury(I) chloride contains the diatomic ion Hg2 2+, so its solubility product expression is [Hg2 2+][Cl-]^2.
Correct Answer
True
True. Hg2Cl2 dissolves into one Hg2 2+ ion and two Cl- ions, not two separate Hg+ ions. The Ksp expression therefore has the Hg2 2+ concentration to the first power and the chloride concentration squared.
Category: Solubility Product
Question 15
Coupled equilibria are two or more equilibrium reactions occurring together that share at least one reactant or product.
Correct Answer
True
True. Because the reactions share a species, a change in one equilibrium shifts the other. Examples include a solid dissolving while one of its ions reacts with an acid or forms a complex ion.
Category: Coupled Equilibria
Question 16
Reversing the dissolution equation of a salt gives a precipitation reaction whose equilibrium constant is 1/Ksp.
Correct Answer
True
True. Writing any reaction in reverse inverts its equilibrium constant. Since Ksp values are usually very small, the K for precipitation from the ions is very large.
Category: Coupled Equilibria
Question 17
For a salt that releases one cation and one anion, such as AgBr, the molar solubility in pure water equals the numerical value of Ksp.
Correct Answer
False
False. For a 1:1 salt, Ksp = s x s = s^2, so the molar solubility is the square root of Ksp, a much larger number than Ksp itself.
Category: Molar Solubility
Question 18
In a saturated solution of a slightly soluble salt, dissolution of the solid has stopped completely.
Correct Answer
False
False. Solubility equilibrium is dynamic: the solid keeps dissolving while ions keep precipitating, and the two processes occur at equal rates, so the concentrations stay constant.
Category: Solubility Product
Question 19
Ammonia acts as a Lewis acid when it bonds to H+ to form the ammonium ion.
Correct Answer
False
False. Ammonia donates the lone pair on its nitrogen atom to H+, so it acts as a Lewis base. The hydrogen ion accepts the pair and is the Lewis acid.
Category: Lewis Acids and Bases
Question 20
The dissociation constant Kd of a complex ion describes how readily the complex forms from its metal ion and ligands.
Correct Answer
False
False. Kd describes the breakdown of the complex into its metal ion and ligands. The formation constant Kf describes the formation reaction, and Kd = 1/Kf.
Category: Complex Ions