1
Q
electrostatic potential energy
A
- E is proportional to (Q1Q2)/d
- E is neg when Qs have opposite signs
- so…E is neg for all salt
- When ions are far apart, d is large and E is a small neg #
- When ions are close together in a salt, d is small, Qs are large, and E is a large neg #
- This means lower energy
- energetically favorable
- E is neg when Qs have opposite signs
2
Q
enthalpy of solution(deltaHsoln)
A
- the overall energy change in enthalpy when an ionic solute is dissolved in a polar solvent
- deltaHsoln=deltaHion-ion+deltaHdipole-dipole+deltaHion-dipole
- overall change in enthalpy when an ionic solute is dissolved in a polar solvent
3
Q
enthalpy of hydration
A
- the energy change when gas-phase ions dissolve in a solvent
- deltaHhydration=deltaHdipole-dipole+deltaHion-dipole
- deltaHsoln=deltaHion-ion+deltaHhydration
4
Q
lattice energy(U)
A
- the enthalpy change that occurs when 1 mole of an ionic compound forms from its free ions in the gas phase
- U=k(Q1Q2)/d
- deltaHsoln=deltaHhydration - U
- U is negative: it is heat released as a crystal is formed
5
Q
Born-Haber cycle
A
- a series of steps with corresponding enthalpy chanes that describes the formation of an ionic solid from its constituent elements
6
Q
Vapor pressure of solutions
A
- At a given temperature, the vapor pressure of the solvent in a solution containing nonvolatile solutes is less than the vapor pressure of the pure solvent.
- When seawater and pure water are adjoined in a sealed container, the seawater side will increase in volume over time
- pure water tranfers over b/c of dissolved solutes in seawater
- As the water in both sections evaporates, the concentration of water vapor in the air space of the sealed chamber increases
- as the concentration of water vapor increases, the pressure the water vapor exerts on the 2 liquid surfaces increases
- At constant temp, this pressure stabilizes at a value equal to the vapor pressure of water at that temp
- rate of evap=rate of condens
- Pure water has a higher rate of evap b/c it moved over
- but, condens rates are the same meaning pure water loser more water than it can restore over time
7
Q
Raoult’s Law
A
- Psoln=XsolventPosolvent
- ideal solution: a solution that obeys Raoult’s law
- solute and solvent experience similar intermolecular forces
- most solns are ideal systems
- solute and solvent experience similar intermolecular forces
8
Q
fractional distillation
A
- a method of separating a mixture of compounds based on their different boiling points
- separates the volatile components of a mixture
- based on observation that bp of a mixture changes as the mixture is distilled
- separates the volatile components of a mixture
9
Q
colligative properties
A
- characteristics of solutions that depend on the concentration and not the identity of particles dissolved in the solvent
10
Q
molality(m)
A
- concentration as mol of solute/kg of solvent
- used to quantify colligative properties
11
Q
Van’t Hoff Factor
A
- Electrolytes dissociate, nonelectrolytes do not
12
Q
ion pair
A
- a cluster formed when a cation and an anion associate with each other in solution
- more form when concentration increases
*
- more form when concentration increases
13
Q
Osmosis
A
- the flow of a fluid through a semipermeable membrane to balance the concentration of solutes in solutions on the 2 sides of the membrane
- flow goes from more dilute to more concentrated
- semipermeable membrances allow particles of solvent to pass through, but not of solute
14
Q
osmotic pressure
A
- the pressure applied across a semipermeable membrane to stop the flow of solvent from less conc to higher conc(aka backwards)
- osmotic pressure increases with solute conc(M) and solution temp(T)
15
Q
reverse osmosis
A
- a process in which solvent is forced through semipermeable membranes, leaving a more concentrated solution behind
