Oceans

• What is a hydrated ion?


  An ion that is surrounded by water molecules
• What is the enthalpy change of solution (ΔsolH)?


  The enthalpy change when 1 mole of an ionic substance dissolves in enough solution to form an infinitely dilute solution.
• What is an infinitely dilute solution?

  One which contains so much solvent that when you add more liquid, there is no change in concentration.
• What is lattice enthalpy (ΔLEH)?


  The enthalpy change when 1 mole of an ionic lattice is formed from its gaseous ions under standard conditions.
• What is the enthalpy change of hydration of ions (ΔhydH)?

  The enthalpy change when 1 mole of aqueous ions is formed from gaseous ions.
• How do you draw enthalpy cycles?


  1. Put the ionic lattice and the dissolved ions on the top and connect them by the enthalpy change of solution (makes the direct route).

  2. Connect ionic lattice to the gaseous ions by the reverse of the lattice enthalpy.

  3. Connect the gaseous ions to the dissolved ions by the hydration enthalpies of each ion to complete the indirect route.

  
• How do you draw an enthalpy level cycle?

  1. Start with the enthalpy of solution (this is direct route).

  2. Put the reverse of the lattice enthalpy above this.

  3. The enthalpies of hydration go from an arrow from the gaseous ions to the dissolved ions.

  
• How do you measure the energy transferred in experiments?

  Use the q=mcΔT equation
• What happens the greater the charge density of ions?

  The greater the electrostatic attraction
• What happens the more exothermic the lattice enthalpy?


  The greater the attraction of water molecules and the more exothermic the hydration enthalpy.
• What is entropy?


  A measure of the number of ways that particles can be arranged and the number of ways that the energy can be shared out between particles.
• What is quanta?


  A measure of energy and a fixed 'package' of energy
• What happens the more energy quanta a substance has?

  The more ways they can be arranged and the greater the entropy.
• What physical state has the lowest entropy and why?


  Solid as they wobble about a fixed point so there isn't much disorder.
• What physical state has the highest entropy and why?

  Gas as gas particles move around wherever they like so they have the most disordered arrangement.
• Does more or less particles mean more entropy and why?

  The more particles you've got, the more ways they and their energy can be arranged, entropy increases when the number of moles increases.
• What is the Brønsted-Lowry theory of acids and bases?


  Acids are proton donors and bases are proton acceptors
• What is a conjugate acid?


  The species that is formed when a Bronsted-Lowry base gains a proton
• What is a conjugate base?


  The species that remains after a Bronsted-Lowry acid has given up a proton
• What is a conjugate pair?


  Species that are linked by the transfer of a proton.

  
• What is a strong acid?


  An acid that is completely ionised in aqueous solution.
• What is a strong base?

  A base that completely ionises in solution.
• Give the equation for NaOH ionising in water.

  NaOH(s)+water⟶Na+(aq)+OH−(aq)
• Give the equation for HCl ionising in water.

  HCl(g)+water→H⁺(aq)+Cl−(aq)
• What determines the relative solubility of a solute?


  - ability to form hydrogen bonds makes it very soluble

  - ion dipole bonds form between water and dissolved ions with delta charges and are strong enough to pull ions from lattice so it dissolves

  - like dissolves like

  - unless ionic bonds in lattice are really strong, the ion-dipole bonds will be strong enough to pull the lattice apart
• How do ionic compounds dissolve in water?


  - the O-H bond is very polar so H has partial positive charge and O has partial negative, this means that ion-dipole bonds can form between water molecules and dissolved ions

  - the partial positive H attracts negative ions, partial negative O attracts positive ions

  - ions separate from ionic lattice and become surrounded by water molecules
• ΔtotS =


  ΔsysS + ΔsurrS
• ΔsurrS =


  -ΔH/T
• ΔsysS =


  Sproducts - Sreactants
• What is the solubility product?

  Ksp, the equilibrium constant for a saturated solution of a sparingly soluble solid in water
• Ksp =


  AaBb -> aA+b + bB-a

  [prodA^b+ (aq)][prodB^a- (aq)]
• What is a sparingly soluble solid?

  a solid that only dissolves a little bit
• What happens when a sparingly soluble solid is dissolved in water?

  it gives a saturated solution where equilibrium is established between the undissolved solid and the dissolved ions
• What are the units of solubility?

  g dm-3
• How do you work out Ksp?


  - write an expression for Ksp

  - find the solubility in mol dm-3

  - find the ratio of moles at equilibrium

  - substitute into the equation

  - work out the units like how you would with Kc
• What is a weak acid?

  An acid that is only partially ionised in aqueous solution
• What is the equation for a weak acid dissociating?

  HA ⇌ H+ + A-
• What is Ka?


  acid dissociation constant for weak acids
• How do you work out pKa?


  -logKa
• How do you work out Ka from pKa?


  10^-pKa