AP Chemistry: 3.10 Solubility - Exam Style questions with Answer- MCQ

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Question

Methanol, $CH_3OH$, dissolves completely in water to form a solution that does not conduct electricity. Which of the following diagrams best shows the major type of attractive force that exists between the particles in the solution?

▶️Answer/Explanation

Ans: C

Water and methanol exhibit hydrogen bonding. Hydrogen bonding is a dipole-dipole interaction that occurs between an $H$ atom bonded to a highly electronegative atom ( $O$ , $F$ , or $N$ ) and an electronegative atom in a nearby molecule. Methanol, being a molecular compound, does not ionize in water and will not form aqueous solutions that conduct electricity.

Question

A student adds a $1 g$ sample of an unknown, brittle solid to distilled water, stirs the mixture, and then measures its conductivity. The student repeats this procedure with more samples of the unknown solid and then produces the graph above. Which of the following statements about the graph and the properties of the solid is correct?

A The increase in conductivity indicates that the unknown is an ionic solid that dissociates into ions when it dissolves in water.

B The increase in conductivity indicates that the unknown is a network covalent solid that ionizes in water.

C The straight line plot indicates that the unknown solid is infinitely soluble in water.

D The straight line plot indicates that the unknown solid has a very low solubility in water.

▶️Answer/Explanation

Ans: A

Since the solid is brittle and the solution conducts electricity, the unknown solid must be an ionic solid. When an ionic solid dissolves in water, it dissociates and the ions are free to move around in the solution, resulting in the conduction of electricity.

Question

Which of the diagrams above best represents the interactions that are responsible for the relatively large solubility of $KCl$ crystals in water, and why?

A Diagram 1, because strong ion-dipole interactions between

KCl

and water help to dissociate the solute.

B Diagram 1, because strong London dispersion forces between the

K^{+}

and

{Cl}^{-}

ions and water replace the weak London dispersion forces between two water molecules.

C Diagram 2, because strong dipole-dipole forces between

KCl

and water help to separate the

KCl

units within the crystals.

D Diagram 2, because the hydrogen bonds between water molecules expand to accommodate the

KCl

particles and pull them into solution.

▶️Answer/Explanation

Ans:A

As $KCl$ dissolves in water, the strong ion-dipole forces between $K^{+}$ ions and $H 2 O$ molecules and ${Cl}^{-}$ ions and $H 2 O$ molecules help dissociate the ionic solid and overcome the hydrogen bonding forces between $H 2 O$ molecules.

Question

Which of the following molecules is least soluble in water?

▶️Answer/Explanation

Ans:C

Question.

On the basis of molecular structure and bond polarity, which of the following compounds is most likely to have the greatest solubility in water?

(A) $CH_{4}$

(B) $CCI_{4}$

(D) $PH_{3}$

▶️Answer/Explanation

Ans:D

Question are based on the information in the table below.

Question

Based on the structural formulas, which of the following identifies the compound that is more soluble in water and best helps to explain why?
(A) Ethane, because the electron clouds of its molecules are more polarizable than those of propanol.
(B) Ethane, because its molecules can fit into the spaces between water molecules more easily than those of propanol can.
(C) Propanol, because its molecules have a greater mass than the molecules of ethane have.
(D) Propanol, because its molecules can form hydrogen bonds with water molecules but those of ethane cannot

▶️Answer/Explanation

.Ans:D

Question

The saturated$ CuSO_4$(aq) shown above is left uncovered on a lab bench at a constant temperature. As the solution evaporates, 1.0 mL samples of the solution are removed every three
days and the $[SO_{4} ^{2-}]$ in the samples is measured. It is observed that the $[SO_{4}^{2-}]$ in the solution did not change over time. Which of the following best helps to explain the observation?
(A) As the solution evaporates, $Cu^{2+}$(aq) and $SO_{4} ^{2-}$(aq) leave the beaker along with the water molecules.
(B) As the solution evaporates, the dissolution of $CuSO_{4}$(s) in the beaker decreases.
(C) The evaporation of water is endothermic, so more $CuSO_{4}$(s) dissolves exothermically in the solution, which increases the$ [SO_{4}^{2-}]$.
(D) As water evaporates, more$ CuSO_{4}$(s) precipitates out of the solution in the beaker.

▶️Answer/Explanation

Ans:B

AP Chemistry: 3.10 Solubility – Exam Style questions with Answer- MCQ

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