Oceans

Question 1

Lattice enthalpy

Answer 1

The enthalpy change when one mole of solid is forked by the coming together of separate ions

Lattice enthalpies are large negative values so -LE is stated when a positive value is needed

Question 2

What effects lattice enthalpy

Answer 2

Lattice enthalpies become more negative as:

• the ionic charge increases
• the ionic radii decreases

Question 3

Enthalpy change of hydration

Answer 3

The enthalpy change for the formation of a solution of ions from one mole of gaseous ions

Question 4

Enthalpy change of solution

Answer 4

The enthalpy change one mole of a substance dissolves

Question 5

How the greenhouse effect leads to global warming

Answer 5

• Radiation from the sun, made up of visible and UV, is absorbed by the Earth
• The Earth then warms up and emits IR radiation
• Greenhouse gases present in the troposphere absorb IR radiation
• This increases the vibrational energy of the bonds and causes the molecules to collide
• The kinetic energy of some molecules increases and raises the temperature of the atmosphere
• An increases concentration of greenhouse gases leads to an increases greenhouse effect

Question 6

What is the pH scale

Answer 6

A negative logarithmic scale of the concentration of hydrogen ions

Question 7

What is an acid and what is a base

Answer 7

An acid is something which donates a proton and a base is something with a lone pair which accepts the proton

Question 8

What is a strong acid and how to calculate the pH

Answer 8

A strong acid is one which fully dissociates

pH = -log10([H+])

Question 9

What is a weak acid and how to calculate the pH

Answer 9

A weak acid is one which only partially dissociates

Ka = ([H+][A-]?)/[HA]

Assuming the concentration of H+ equals the concentration of A-

Assuming, at equilibrium, the concentration of HA equals 0.1 mol/dm3

Question 10

What is a buffer solution and how does it work

Answer 10

A buffer solution is one which resists change in pH when small quantities of acid or alkali are added

There must be a large reserve of both acid and conjugate base

Question 11

How to predict if a precipitate will form

Answer 11

If the product of the concentration of the ions is greater than Ksp, it will precipitate

If the product of the concentration of the ions is less than Ksp, it will not precipitate

Question 12

Entropy

Answer 12

A measure of the number of ways of arranging molecules and distributing energy

A collection of molecules has a higher entropy if:

• The molecules are more spread out
• The energy is shared amount more molecules

Question 13

Total entropy = ?

Answer 13

Entropy of the system + Entropy of the surroundings

Entropy of the surroundings = -(Enthalpy change/Temperature)