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OCR A-Level Chemistry Salters B > Oceans > Flashcards

Flashcards in Oceans Deck (13)
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1

Lattice enthalpy

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

2

What effects lattice enthalpy

Lattice enthalpies become more negative as:
-the ionic charge increases
-the ionic radii decreases

3

Enthalpy change of hydration

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

4

Enthalpy change of solution

The enthalpy change one mole of a substance dissolves

5

How the greenhouse effect leads to global warming

-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

6

What is the pH scale

A negative logarithmic scale of the concentration of hydrogen ions

7

What is an acid and what is a base

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

8

What is a strong acid and how to calculate the pH

A strong acid is one which fully dissociates

pH = -log10([H+])

9

What is a weak acid and how to calculate the pH

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

10

What is a buffer solution and how does it work

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

11

How to predict if a precipitate will form

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

12

Entropy

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

13

Total entropy = ?

Entropy of the system + Entropy of the surroundings

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