Factors That Affect Dissolving and Solubility Flashcards
(12 cards)
Rate of Dissolving
A reflection of how quickly or slowly a solute can dissolve in a solvent
Temperature
Solutes dissolve faster in warmer temperatures
This is due to greater kinetic energy, which increases the number of collisions between molecules so they break apart into the solvent faster
The one exception are gases, whose solubility actually decreases with higher temperatures because it allows the gas molecules to escape from the liquid
Agitation
Stirring or shaking a mixture increases the rate of dissolving
Agitation brings fresh solvent into contact with undissolved solute
Size of Particles
Decreasing the size of solute particles increases the rate of dissolving
This increases the surface area of solute that is exposed to the solvent
Pressure
Pressure does not affect the solubility of solid and liquid solutions, because they cannot be compressed!
The solubility of a gas is proportional to the pressure of the gas above the liquid
Pushes more gas molecules into the liquid increasing the frequency
Basic Rule of Solubility
The simple rule is “like dissolves like”
Polar compounds can only be dissolved in polar solvents and non-polar compounds can only be dissolved in non-polar solvents
What makes a compound polar?
Having large differences in electronegativity among the elements in a compound
The electrons tend to be more attracted to the atom within a bond with the higher electronegativity, making that end relatively negative, and the other end positive
Electronegativity
the tendency of an atom to attract electrons in a molecule
Dipole-Dipole Attractions
This involves the attraction between the opposite charges on two different polar molecules
Intermolecular
Much weaker than ionic and covalent bonds
Denoted with dashed rather than whole lines
Hydrogen Bonding
Hydrogen bonding is much stronger than ordinary dipole-dipole attractions (but still much weaker than covalent bonds)
Occurs when the difference in electronegativity between non-metals in a bond is quite high
Occurs when H is bonded to O, N, or F
Ion-Dipole Attractions
Attractive forces between an ion and a polar molecule
Ionic crystals consist of repeating patterns of oppositely charged ions
When an ionic compound dissolves in water, the negative end of the dipole on some water molecules attracts the cations on the surface of the ionic crystal
The positive end of the water dipole attracts the anions
AN IONIC COMPOUND WILL DISSOLVE IN A POLAR SOLVENT (if it is soluble)
How Do Non-Polar Solutes Dissolve in Non-Polar Solvents?
covalent compounds do not break apart into component ions in solution, so they cannot conduct electricity (NON-ELECTROLYTES), nor can they dissolve in polar solvents
London Forces are the sole force of attraction in non-polar solutions, and these weak forces do allow two non-polar solutions to mix
