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Flashcards in Further energetics Deck (47)
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1

What are Born-Haber cycles used to calculate

Enthalpy changes involving ionic compounds

2

What is the Bond enthalpy

The enthalpy change when one mole of a stated covalent bond in the gaseous state is broken

3

How is the bond strength given in:
a)covalent bonding
b)Ionic bonding


a)Bond enthalpy
b)Lattice enthalpy

4

What is the lattice enthalpy

The energy change when one mole of an ionic solid is formed from its gaseous ions

5

What does the following refer to:
a)Ionisation energies
b)Electron affinities

a)Refers to the formation of positively charged ions
b)Refers to the formation of negatively charged ions

6

What is meant by electron affinity

The energy change when one mole of electrons is gained by one mole of gaseous atoms or anions to form one mole of gaseous anions

7

What is the enthalpy change of atomisation

The enthalpy change when one when a mole of gaseous atoms are formed from an element in its standard states

8

How can you calculate the enthalpy change for ionic compounds

Using the Born-Haber cycle and given data

9

How can you calculate the enthalpy change for covalent compounds

By applying Hess's law which relies on the first law of thermodynamics

10

What is the first law of thermodynamics

The total enthalpy for a reaction is independent of the pathway taken

11

What is the value for the first value for electron affinity

They are negative for almost all elements except for noble gases in which they are positive

12

What is the value for the second value for electron affinity

Almost always positive because of the repulsion between the electron and the anion

13

Why is the first value for electron affinity positive in noble gasses

Due to the repulsion from the electrons in the outer shell

14

What can lattice energy be calculated from

A model of ionic bonding

15

What two things does the polarising power of a cation do

1)increases with increasing charge
2)Increases with decreasing ionic radius

16

What two things does the polarisability of an anion do

1)Increases with increasing charge
2)Increases with increasing ionic radius

17

What does the polarisation of anions lead to

A degree of covalent bonding in ionic compounds

18

What happens the greater the degree of covalent bonding

The larger the percentage difference between the experimental and theoretical lattice energies

19

How can theoretical lattice energies be calculated

Using electrostatic theory and a model of ionic bonding

20

What are the three factors in the ionic model

1)The charge on an electron
2)The number of charges on the ions
3)Distances between the centres of the ions

21

What are three things the ionic model assumes

1)The ions are perfect spheres
2)Their charge is distributed evenly
3)The ions pack together in a regular way

22

What is meant by energy change of solutions

The enthalpy change when one mole of an ionic solid dissolve in excess water to form an infinitely dilute solutions

23

How can the enthalpy of a solution be determined experimentally

Using a calorimeter

24

What is the enthalpy change of hydration

The enthalpy change when one mole of gaseous ions dissolves in excess water to form aqueous ions

25

Why is the value for the enthalpy change of hydration always negative

Because bonds form between ions and water molecules

26

What two factors does the enthalpy change of hydration depend on

1)Ionic charge
2)Ionic radius

27

When does the enthalpy change of hydration become:
a)more negative
b)less negative


a)As the charge increases
b)As the ionic radius increases

28

When do entropy changes occur

During a change in states, dissolving, and chemical reaction

29

What is entropy

A measure of the disorder of a system

30

What are the three factors that affect entropy

1)The number of particles
2)The complexity of the particles
3)How many ways the particles can be arranged