Chapter 8: Solutions

Chemical reactions only occur when molecules or atoms collide/interact with each other
Solutions are a uniform mixture of one or more solutes dissolved in a solvent. * Alloys are solid solutions of two or more metals
Solutions can be described quantitatively by figuring out how much solute is dissolved in a specific amount of solvent, aka concentration * Solubility is the maximum amount of solute that can dissolve in a solvent in grams per liter * Molar solubility is the max amount of solute that can dissolve in a solvent in moles per liter
Qualitative terms can also describe a solution * A concentrated solution is a large amount of solute dissolved in the solvent * A dilute solution has a small amount of dissolved solute * Saturated solutions have the maximum amount of solute dissolved in solvent * Sometimes in equilibrium if there is solid solute in the solution as well * Unsaturated solutions have less than the max amount of solute dissolved in the solvent. * Never any undissolved solute in solution * Supersaturated solution has more than the max amount dissolved * Obtained at a high temperature and carefully cooling to avoid crystallizing * Solution is metastable: can be crystallized if shaked or disturbed

Solutions can be made with a solvent and solute with similar polarities but not with very different polarities
Solution process * Solute molecules separate to allow solute to fit between them. Energy is used to break attraction between solute molecules * Solvent molecules separate to allow solute between them. Energy used to break attraction between solvent molecules * Separated molecules are combined. Energy released when new attractions form between solvent and solute * If more energy is released than used, solvent will dissolve in the solute. Excess energy will release as heat and temperature will increase.
If the solution can have more arrangements or increases in states, it will have high entropy. High entropy helps the solution process

Ionic compounds dissolve into aqueous solutions * The high lattice energy makes it near impossible to dissolve but the highly polar water molecule is attracted to the ions and enough energy is released. * The water molecule attraction releases enough energy so dissolution is favored. * Entropy increases because of the crystal structure breaking up, which helps the solution process

Gasses mix freely with other gasses because of entropy only. * Gasses fill up vacuum containers because increases the amount of possible arrangements it could have, which increases entropy

Heating the solution, grinding up chemicals, and stirring vigorously can increase how fast a solution process occurs * All three of these increases surface area of the solid * Heat increases solvent molecule motion to increase collision speed * Grinding increases solute exposure to solvent * Stirring moves solute away from other solute molecules

Aqueous solutions have water as the solvent * Ionic substances dissociate completely in water * Some ions dissolve through ionization where their solutions can conduct electricity. These are called electrolytes * Weak electrolytes dissociate only slightly and conduct electricity poorly * If the solution does not conduct electricity, these are nonelectrolytes

Strong electrolytes are ionic compounds that are dissolvable in water, such as NaCl, KBr, and Mg(NO3)2
Covalent compounds in the gas state can ionize completely when dissolved in water * Only HCl, HBr, and HI

Molecular compounds that are soluble but only partially ionize * Most ionize less than 10 percent
Weak electrolyte reactions with water results in dynamic equilibrium

Dissolve but don't form ions * sugars like glucose, sucrose, and alcohols such as methanol, ethanol, and propanol

Molarity is the most common unit. * Molarity is number of moles of solute divided by the liters of solvent dissolved in

Most solids are more soluble in hot solvents vs cold solvents
Increasing temperature increases disorder. If a molecule could move from a lower entropy state to a higher entropy state, it would

External pressure has no significant effect on liquid or solid solubility because they are not compressed when pressure is increased
Gasses, when compressed, increase solubility because there is less space for the molecules to be, increasing the frequency of gas molecules converting to liquid
Henry’s law is the solubility of gasses * solubility of a gas = kP * k, Henry’s proportionality constant * P is gas partial pressure