Oceans Flashcards
Define lattice enthalpy
The enthalpy of when one mole of a solid is formed from its ions in its gaseous state
Define the enthalpy change of hydration
The enthalpy change when one mole of
gaseous ions forms a solution of aqueous ions.
What does it mean if water is amphoteric
It is both a base and an acid
Strong acid/base is …
an acid/base that dissociates fully in water
Weak acid/base is …
an acid/base that partially dissociates in water
Entropy is…
a measure of the disorder of a system
What factors determine the relative solubility of a solute in aqueous and non-aqueous solvents?
Temperature
Polarity
Molecular size
What are hydrated ions?
An ion surrounded by water molecules in a spherical shaped shell
What is enthalpy change of solution?
When one mole of ionic solid dissolves in water to form one mole of aqueous ions under standard conditions
How are lattice enthalpy and enthalpy change of hydration affected by charge density of the ions?
The greater the charge density of the ions:
The more exothermic the lattice enthalpy due to increased electrostatic attraction
The more exothermic the hydration enthalpy due to the increased attraction of water molecules.
How to find total entropy change ?
Entropy change of the system + entropy change of the surroundings
How to find entropy change of the surroundings?
Enthalpy change of the reaction is divided by temperature (K)
When is a reaction feasible
When the total entropy change is +ve
How to find the entropy change of the system?
Total sum of products - total sum of reactants
If entropy change is positive the entropy is…
more disordered
If entropy change is negative the entropy is…
less disordered
What is solubility product?
Ksp is an equilibrium constant for a solid dissolving in an aqueous solution, the higher the Ksp value, the more soluble a substance.
What is a conjugate acid - base pair?
A conjugate acid-base pair contains two species that can be easily converted by transferring a proton.
What is a strong acid/base?
An acid/base that completely dissociates in a solution
What is a weak acid/base?
An acid/base that only partially dissociates in a solution
What is a buffer?
A system that can resist pH change when small amounts of an acid/base is added.
How do buffers work?
Ch3COOh = Ch3COO- + H+
Addition of an acid:
More H+ present in the solution so they combine with the salt that acts as a large reservoir to reform the acid. The REVERSE reaction is favoured and the position of equilibrium shifts to the LEFT.
Addition of a base:
More OH- present so they combine with H+ to form water. The FORWARD reaction is favoured and the position of equilibrium shift to the RIGHT.
What is an acid buffer made up of?
Weak acid and a salt of the acid formed from a strong base
What is a basic buffer made from?
Weak base and a salt of the base formed from a strong acid
What assumptions are made when finding Ka ?
[Salt] = [A-]
[Acid] = [HA] as it is only slightly dissociated
What is the ‘greenhouse effect’
- Visible radiation is absorbed by the Earth’s surface causing it to warm up
- Earth’s surface emits IR radiation back into the atmosphere with some escaping into space
- Most IR radiation is absorbed by greenhouse gases which causes their bonds to vibrate more
- Vibrational energy is converted into kinetic energy which warms up the atmosphere
- IR radiation is also re-emitted by molecule which cause the Earth’s surface to warm up.
