O.1

Question 1

How are ions in an ionic solid held together?

Answer 1

By their opposite electrical charges. Each cation attracts several anions and vice versa.

Question 2

What is called when a large number of ions are arranged in fixed positions, held together by electrostatic forces?

Answer 2

Giant ionic lattice.

Question 3

In ionic lattice, which two type of forces compete, and which one is always greater?

Answer 3

Attraction and repulsion. But overall attractions are always greater and therefore the lattice is held together.

Question 4

What are two properties of ionic solid as a result of its strong electrostatic attraction?

Answer 4

They are hard and have high melting and boiling points.

Question 5

What happens to ions in a ionic substance when they dissolve in water?

Answer 5

Ions become surrounded by water molecules and spread out through the water.

Question 6

What is the attraction between water molecules and ions known as?

Answer 6

Ion-dipole interaction.

Question 7

Which part of the water molecule interacts with the cation?

Answer 7

The O.

Question 8

Which part of the water molecule interacts with the anion?

Answer 8

The two Hs.

Question 9

Can ion-dipole interactions be multilayers?

Answer 9

Yes.

Question 10

How many water molecules interact with each ion in the first layer?

Answer 10

Four.

Question 11

Ions in ionic substances are said to be what once they are dissolved in water?

Answer 11

They are separated and behave independently of each other.

Question 12

What are water molecules that surround an ion known as that makes ions hard to move?

Answer 12

A solvation shell.

Question 13

Are all ionic substances soluble in water?

Answer 13

No.

Question 14

What is important in deciding whether an ionic substance will dissolve?

Answer 14

The energy changes involved.

Question 15

What bonds must be broken before ionic substance can dissolve and spread out in the solution?

Answer 15

The electrostatic bonds between ions in the lattice must be broken to separate the ions.

Question 16

Separating the ions by breaking electrostatic bonds is an example of what type of energy change?

Answer 16

Endothermic. So energy is required.

Question 17

What enthalpy change measures the strength of ionic attractions in a lattice?

Answer 17

Lattice enthalpy.

Question 18

What is the symbol representation of lattice enthalpy?

Answer 18

∆H(LE), where LE refers to lattice.

Question 19

What is the definition of lattice enthalpy?

Answer 19

The enthalpy change when one mole of ionic solid is formed by the coming together of the separate ions.

Question 20

What physical state changes are involved in the lattice enthalpy?

Answer 20

From ions in gaseous states to a lattice in solid state.

Question 21

What sign does lattice enthalpy always have?

Answer 21

• negative, lattice enthalpies are always exothermic, because it is a bond making process.

Question 22

The amount of energy you’ll have to put into breaking a lattice is equivalent to what value?

Answer 22

-∆H(LE), this becomes a positive value, as breaking bonds is an endothermic process and require an energy input.

Question 23

What are two factors lattice enthalpies depend on?

Answer 23

• Size of ions

- Charge of ions

Question 24

As the ionic charges increase, what happens to the value of the lattice enthalpy?

Answer 24

It becomes more exothermic.

Question 25

As the ionic radii, increase, so ion gets bigger, what happens to the value of lattice enthalpy?

Answer 25

It becomes more endothermic.

Question 26

So, bigger ionic charges and smaller ionic radii means a more exothermic lattice enthalpy. How can these two factors be summaries to one?

Answer 26

The higher the charge density, the more exothermic the lattice enthalpy.

Question 27

Large negative lattice enthalpy can suggest what about a substance's solubility?

Answer 27

They are usually insoluble.

Question 28

When a ionic solid is placed in water, where does ion-dipole interaction happen first?

Answer 28

On the surface, where surface ions become separated and surrounded by water molecules.

Question 29

When an ion is in solution, and surrounded by water molecules, what is it said to be?

Answer 29

Hydrated.

Question 30

What impact will high charge density of an ion have on the size of the hydrated ion in solution?

Answer 30

The higher the charge density, the bigger the hydrated ion will be because the more water molecules will be attracted.

Question 31

When ion-dipole bond forms, what energy change is involved?

Answer 31

Exothermic, the process releases energy.

Question 32

Does all the energy released through the forming of ion-dipole bonds go into breaking electrostatic bonds in the lattice?

Answer 32

No, some also go on to break the strong hydrogen bonding between water molecules.

Question 33

What enthalpy change measures the strength of attraction between ions and water molecules?

Answer 33

Enthalpy change of hydration.

Question 34

What is the symbol representation of the enthalpy change of hydration?

Answer 34

∆H(hyd), where hyd refers to hydration.

Question 35

What is the definition of the enthalpy change of hydration?

Answer 35

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

Question 36

What physical state changes are involved in the enthalpy change of hydration?

Answer 36

From ions in gaseous state to ions in solution.

Question 37

What sign does the enthalpy change of hydration always have?

Answer 37

- negative, hydration is exothermic and energy is released.

Question 38

What are two factor enthalpy change of hydration depends on?

Answer 38

- Ionic charges | - Ionic radii

Question 39

As the charge density of ion increase, what happens to the value of the enthalpy change of hydration?

Answer 39

It gets more exothermic.

Question 40

What enthalpy change is used when the solvent is not water?

Answer 40

Enthalpy of solvation, ∆H(solv).

Question 41

What enthalpy change can be derived from finding the difference between the enthalpy change of hydration and the lattice enthalpy?

Answer 41

The enthalpy change of solution.

Question 42

What is the symbol representation of the enthalpy change of solution?

Answer 42

∆H(solu), where solu refers to solution.

Question 43

What is the definition of the enthalpy change of solution?

Answer 43

The enthalpy change when one mole of solute dissolves to form a very dilute solution.

Question 44

How can the enthalpy change of solution be found?

Answer 44

It can be measured experimentally.

Question 45

What is the equation that enables you to find the enthalpy change of solution from the lattice enthalpy and enthalpy changes of hydration?

Answer 45

∆H(solu) = ∆H(hyd, cation) + ∆H(had, anion) - ∆H(LE)

Question 46

When is the enthalpy change of solution negative?

Answer 46

When the sums of enthalpy changes of hydration is bigger than the lattice enthalpy.

Question 47

When the enthalpy change of solution is negative, and therefore the dissolving process is exothermic, what does this mean about the solubility of the substance?

Answer 47

The substance normally dissolves, giving out some energy is the process.

Question 48

When is the enthalpy change of solution positive?

Answer 48

When the sums of enthalpy changes of hydration is smaller than the lattice enthalpy.

Question 49

When the enthalpy change of solution is a large positive value, so the process of dissolving is very endothermic, what does this mean about the solubility of the substance?

Answer 49

The substance does not dissolve, because the process requires more energy and is energetically unfavorable.

Question 50

When the enthalpy change of solution is slightly positive, so a little bit endothermic, what does this mean about the solubility of the substance?

Answer 50

The substance will normally still dissolve, despite the process seems to be energetically unfavorable.