Solutions (General Chemistry: Chapter 9)

Question 1

What is a solution?

Answer 1

A solution is a homogenous (the same throughout) mixtures of two or more substances that combine to form a final phase, usually the liquid phase.

• Solutions can be formed from different combinations of the three phases of matter

Question 2

What is solvation?

Answer 2

Solvation, also known as dissolution, is the electrostatic interaction between solute and solvent molecules.

• If the new interactions are stronger (more stable) than the original ones (between solute and solute or between solvent and solvent), sovlation is exothermic (also is exergonic (delta G < 0 ))
• Most dissolutions (solvations) are endothermic as the new interactions are weaker than the original ones.

Question 3

What is the difference between exothermic/endothermic and exergonic/endergonic?

Answer 3

Exothermic/endothermic describes the flow of heat in relation to the system, while exergonic/endergonic describes if the process is spontaneous or nonspontaneous.

Question 4

What is an ideal solution?

Answer 4

An ideal solution is a solution that is formed from new interactions approximately equal to the overall strength of the orinal interactions.

• Ideal solutions = (delta H = 0)

Question 5

What is a coordination bond?

Answer 5

A coordination bond is formed when an electron pair is donated from a single molecule.

Question 6

What is a complex ion and how does it relate to ligands?

Answer 6

A complex ion (also known as a coordination compound) refers to a molecule in which one cation is bonded to at least one electron pair donor (ligand).

• The electron pair donor in a complexation reaction is called a ligand
  
  • There can be multiple ligands.
• Complex ions are held together by coordinate covalent bonds.
  
  • Ligands are lewis bases since they donate a pair of electrons

Question 7

How does temperature affect solubility in a solid and in a gas?

Answer 7

Solubility of solids can be increased by increasing temperature. Solubility of gases can be increased by decreasing temperature or by increasing the partial pressure of the gas above the solvent.

• Solvent in this scenario is a liquid

Question 8

What are the ions constituting salts that are always soluble?

Answer 8

Group 1 metals (Na, Li, K, etc..), ammonium (NH₃⁺), nitrate (NO₃^-), and acetate (CH₃COO^-) salts are always soluble.

Question 9

What is the difference between molarity and molality?

Answer 9

The difference between molarity and molality is: molarity is divided by the # of L (liters) of solution and molality is divided by the number of kg (kilograms) of solution.

Question 10

How can a salt with an incredibly small K_sp (will not dissolve), be dissolved in solution?

Answer 10

Coupling unfavorable solubility salts with favorable formation of complex ions (increased K_f) will drive the dissolution (solvation) of the salt.

• A reactions with a high K_f value drives the dissolution of the salt despite an incredibly small K_sp by utilizing La Chatelier’s Principle.

Question 11

What is the common ion effect?

Answer 11

The common ion effect occurs when an ionic contituent of a compound is already dissolved in solution decreasing the the solubility of the compound when it is added to the solution.

• This occurs due to La Chatelier’s Principle.