LECTURE 17 ION POLARISATION and SOLUBILITY by Pooganeswari Siteram Pillai

Arwen

2021-11-15 13:06:23 UTC

going down group 2:
• thermal stability de

Benedict JC2T

2021-11-15 13:07:10 UTC

ION POLARISATION
- Ability to attract electrons and distort an anion is called polarizing power of cation

FACTORS
-smaller cation
-higher charge density
-anion is larger
- anion having more negative charge

THERMAL STABILITY OF GROUP 2 NITRATES AND CARBONATES

more stable - more difficult to decompose
*Thermal stability increases as ion polarity decreases
ex: Magnesium carbonate is less thermally stable than barium carbonate as the anions are more distorted in magnesium carbonate causing the bonds to weaken

LATTICE ENERGY, ENTHALPY OF SOLUTION AND ENTHALPY OF HYDRATION

Lattice energy - always negative
Enthalpy of solution - positive or negative (largely positive means insoluble)
Enthalpy of Hydration - always negative

lattice + solution = hydration

SOLUBLITY OF GROUP 2 SULFATES AND HYDROXIDES

- Solubility of sulfates decrease down the group
- Solbulity of hydroxides increases down the group

CHANGE IN HYDRATION ENERGY DOWN THE GROUP

-if same charge
-smaller ions have greater enthalpy of hydration
-enthalpy of hydration decreases from magnesium, calcium, strontium and barium ions (Enthalpy change becomes less negative down the group)

CHANGE IN LATTICE ENERGY DOWN THE GROUP

-if the ions are the same charge
-lattice energy is greater if ions are small
-lattice energy decreases down the group
-inversely proportional to radius

GROUP 2 SULFATES (going down the group)
- Lattice energy becomes more positive
- enthalpy change of hydration becomes more negative
- enthalpy change of solution becomes more positive (less soluble)

GROUP 2 HYDROXIDES (going down the group)
- lattice energy vecomes more negative
- enthalpy change of hydration becomes more negative
- enthalpy change of solution becomes more negative (more soluble)

I need to revise more on the equations in deciding whether the ions are more soluble or not. (get used to calculating it)

Jasmine JC2T

2021-11-15 13:48:21 UTC

Learnt :
- ion polarization
- factors affecting polarization ( mostly charge density is being discussed )
- thermal stability of group 2 carbonates and nitrates
- lattice energy, enthalpy solution, and enthalpy of hydration
- solubility of group 2 sulfates and hydroxides

Need to revise more on :
- lattice energy and enthalpies

Teaching was good and detailed.

Frederic JC2T

2021-11-15 14:29:19 UTC

-Ion polarisation
-Factors:
Radius of atom and charge density
Thermal stability of sulfates and hydroxides
Sulfates have a higher decrease in hydration energy thus enthalphy of solution is higher and solubility decreases down the group while hydroxides have a higher decrease in lattice energy thus enthalpy change of solution decreases and solubility increases down the group

Formula: hydration= solution + lattice

Jacksen JC2T

2021-11-15 16:05:13 UTC

- ion polarization
- factors affecting it
- thermal stability
- revised about lattice energy/ enthalpy change of solution and hydration
- their trend down group

- ngl lecture was a bit weird cuz its a mix of new chapters and old ones

Juliano JC2T

2021-11-16 02:11:20 UTC

-ion polarisation
-affect by size and charge of the ion.
-thermal stability of group 2 carbonate and nitrate and the explaination.
-solubility of group 2 hydroxide and sulfate

Megan JC2T

2021-11-16 02:12:44 UTC

- Ion polarisation
- Factors affecting polarisation :
1. Small cation
2. Higher positive charge
3. Anion is large
4. Anion having more negative charge
- Thermal stability of group 2 carbonates increases down the group because the polarising power of carbonates increases down the group.
- Thermal stability of gropup 2 nitrates increasesincrease because the smaller ion is a stronger the polarising power and makes it easier to decompose.
- Reviewed about formula : Latt + Sol = Hyd
- Enthalpy of hydration decreases more in group 2 sulfates compared to group 2 hydroxides.
- Lattice energy decreases more in group 2 hydroxides compares to group 2 sulfates.

Thomson

2021-11-16 02:19:07 UTC

Ion polarisation depends on charge density which depends on radius of atom and charge of atom

thermal stability of group 2 sulphate and hydroxide (affected by ion polarisation)

lattice energy + solution = hydration

solubility of sulphate (hydration affected more) and hydroxide (lattice energy affected more)

Kenneth JC2G

2021-11-16 06:51:48 UTC

1. What are the factors that affect ion polarisation?

Small cation size
More positive charge
Big anion size
More negative charge

2. How ion polarisation affects thermal stability of both Group 2 carbonates and nitrates?

Smaller cation - more polarising power
Can distort the bond between anion bonds
More ion polarisation = easier decomposition
More ion polarisation, thermal stability increase

3. What have you learned about solubility of sulfates and hydroxides down the group 2 in AS?

Sulfates decrease down the group
Hydroxides increase down the group

4. Relate lattice energy, enthalpy of hydration and enthalpy of solution with the trend of solubility of sulfates down Group 2

Solubility of sulfates decreases down the group because both lattice energy and enthalpy of hydration decreases in magnitude, but enthalpy of hydration decreases more than lattice energy, making enthalpy of solubility more positive.

5. Relate lattice energy, enthalpy of hydration and enthalpy of solution with the trend of solubility of hydroxides down Group 2

Solubility of hydroxides increases down the group because lattice energy decreases by larger calule, enthalpy change of hydration decreases by smaller value, making the solubility increases.

Lindsay JC2G

2021-11-16 06:52:30 UTC

What are the factors that affect ion polarisation?

Small cation size
More positive charge
Big anion size
More negative charge

How ion polarisation affects thermal stability of both Group 2 carbonates and nitrates?

Smaller cation - more polarising power
Can distort the bond between anion bonds
More ion polarisation = easier decomposition
More ion polarisation, thermal stability increase

What have you learned about solubility of sulfates and hydroxides down the group 2 in AS?

Sulfates decrease down the group
Hydroxides increase down the group

Relate lattice energy, enthalpy of hydration and enthalpy of solution with the trend of solubility of sulfates down Group 2

Solubility of sulfates decreases down the group because both lattice energy and enthalpy of hydration decreases in magnitude, but enthalpy of hydration decreases more than lattice energy, making enthalpy of solubility more positive.

Relate lattice energy, enthalpy of hydration and enthalpy of solution with the trend of solubility of hydroxides down Group 2

Solubility of hydroxides increases down the group because lattice energy decreases by larger value, enthalpy change of hydration decreases by smaller value, making the solubility increases.

Davis JC2G

2021-11-16 06:55:01 UTC

The factors that affect ion polarisation

Small cation size
More positive charge
Big anion size
More negative charge

How does ion polarisation affects thermal stability of both Group 2 carbonates and nitrates?

Smaller cation - more polarising power
Can distort the bond between anion bonds
More ion polarisation = easier decomposition
More ion polarisation, thermal stability increase

Solubility of sulfates and hydroxides down the group 2 in AS?

Sulfates decrease down the group
Hydroxides increase down the group

Relate lattice energy, enthalpy of hydration and enthalpy of solution with the trend of solubility of sulfates down Group 2

Solubility of sulfates decreases down the group because both lattice energy and enthalpy of hydration decreases in magnitude, but enthalpy of hydration decreases more than lattice energy, making enthalpy of solubility more positive.

Relate lattice energy, enthalpy of hydration and enthalpy of solution with the trend of solubility of hydroxides down Group 2

Solubility of hydroxides increases down the group because lattice energy decreases by larger value, enthalpy change of hydration decreases by smaller value, making the solubility increases.

Kendrew JC2G

2021-11-16 06:58:56 UTC

Factors that affect ion polarisation

Small cation size
More positive charge
Big anion size
More negative charge

How ion polarisation affects thermal stability of both Group 2 carbonates and nitrates?

Smaller cation - more polarising power
Can distort the bond between anion bonds
More ion polarisation = easier decomposition
More ion polarisation, thermal stability increase

The solubility of sulfates and hydroxides down the group 2 in AS

Sulfates decrease down the group
Hydroxides increase down the group

Relate lattice energy, enthalpy of hydration and enthalpy of solution with the trend of solubility of sulfates down Group 2

Solubility of sulfates decreases down the group because both lattice energy and enthalpy of hydration decreases in magnitude, but enthalpy of hydration decreases more than lattice energy, making enthalpy of solubility more positive.

Relate lattice energy, enthalpy of hydration and enthalpy of solution with the trend of solubility of hydroxides down Group 2

Solubility of hydroxides increases down the group because lattice energy decreases by larger value, enthalpy change of hydration decreases by smaller value, making the solubility increases.

Keira JC2G

2021-11-16 07:11:51 UTC

From this lecture, I learned:

Factors affecting ion polarisation:
1. Small cation
2. Higher positive charge
3. Bigger anion
4. More negative charge

Ion polarisation affecting thermal stability
- smaller cation results in more polarising power
- which can distort the bond between anions
- more ion polarisation allows easier decomposition and decreases stability

Lattice energy and enthalpy of solution and hydration
- solubility of sulfates decrease down group 2 since lattice energy decrease less than enthalpy of hydration decrease in magnitude, making the enthalpy of solubility more positive
- solubility of hydroxides increase down the group since the lattice energy decrease by a larger value than the enthalpy of hydration, increasing solubility

I think the teaching was clear and easy to follow, and the videos helped in revising for this topic. However, I still need to practice more to know what questions will be expected.

Ella JC2G

2021-11-16 07:35:04 UTC

I have learnt the following concepts:

Ionisation Energy

Polarising power of cation and polarisability of anion
Results in the distortion of the electron cloud

Factors Affecting Ion Polarisation

(More polarised if:) small cation of high + charge
(More polarised if:) large anion of high - charge

Thermal Stability of Nitrates and Carbonates

Increases down the group
Ion polarisation decreases as cation size increases
The carbon-oxygen bond is more easily broken

Solubility of Sulfates

Both LE and HE become more endothermic
The increase in value of HE is greater
LE = HE - sol
When HE increases out of proportion, sol must also increase
Sol becomes more endothermic and becomes less soluble

Solubility of Hydroxides

Both LE and HE become more endothermic
The increase in value of LE is greater
LE = HE - sol
When LE increases out of proportion, sol must decrease
Sol becomes more exothermic and becomes more soluble

Overall, the lecture was understandable and elaborate. I think I would need to practise more with PEQ.

Jonathan

2021-11-16 13:06:20 UTC

The factors that affect polarisation are the charge and size of the ion. I also learned how the polarisation affects the thermal stabillity of group 2 carbonates and nitrates, and how the trend of solubility of group 2 sulfates and hydroxides are, and why this is like this due to enthalpy of hydration and solubility.

Ashley JC2G

2021-11-16 13:25:28 UTC

- Ion polarisation and its factors!
for cation: higher charge density = higher ion polarisation
for anion: larger radius, smaller charge
- How ion polarisation affects thermal stability, solubility of sulfates and hydroxides
- basically down Group 2, more thermally stable, bc less ion polarization = less bonds distorted thus harder to break
- Let your Soul go and Hide:
Lattice + Solution = Hydration
- And also the trends of each enthalpy change down the groups ++ explanation why

WHICH I WILL NOW TEACH ! ! ! !
(we're using common example of sulfates)

Lattice Energy depends on the SUM of radius of both cation and anion. ( there's only one equation involving both ) Bc sulfate ion is very large, the increase in cation radius = not very significant increases. bc L.E is inversely proportional to the SUM of the radius, that means that the decrease in lattice energy is not so much as compared to the

ENTHALPY CHANGE OF HYDRATION ! ! ! !
which is inversely proportional to the radius size of the cation! (given that the anion used stays the same going down the group) Their decreases are much more dramatic (or like,, very big changes). Therefore, enthalpy change of solution INCREASES = LESS SOLUBLE DOWN THE GROUP

~ psst for hydroxides, enthalpy change of solution decreases down the group, bc enthalpy change of hydration decreases by a smaller amount, enthalpy change of lattice decrease by a larger amount. bc of the hydroxide ion being a small ion (?) ~

- Also was reminded that high positive enthalpy change of solution = insoluble
low or small positive enthalpy change of solution = soluble

the lecture was pretty cool, i wish we could do some more practice questions later on now that i finally understand, but yay transition metals!! can't wait thanks sirr

James JC2G

2021-11-16 13:48:21 UTC

Ion polarisation factors
1. more negative or positive charge
2. big or small cation size

what affects thermal stability due to ion polarisation
a smaller cation means that there is more polarising power which distorts the bonds between the anions and thus allowing easier decomposition and decreases stability

Relationship between lattice energy, enthalpy of hydration and solution, and trend of solubility of sulphates going down group 2
- solubility decrease further down the group as lattice energy decreases less than the enthalpy of hydration decreases in magnitude making the solubility positive, while solubility of hydroxide increases down the group as the lattice energy decreases more than the hydration increasing the solubility

(Note to self: revise pyp)

Elizabeth Donna

2021-11-16 14:38:45 UTC

- Ion polarization : Depends on charge density
* More positive or negative charge
* Big or Small Cation
- Charge Density : Depends on Radius of atom and the Charged of the atom

Lattice Energy + Solution --> Hydration

Review the concept of solubility of sulfate and hydroxide going down the group and now using that relate it to lattice energy, enthalpy of hydration and solution

Review :
1.Textbook
2.Example questions

Angela JC2G

2021-11-16 16:30:11 UTC

Ion polarisation

Positive charges on the cation may attract electrons in the anion, resulting in distortion of the electron cloud
Polarizing power of cation: ability to attract electrons and distort an anion

Factors affecting ion polarisation

small cation, higher positive charge, so higher charge density
large anion, more negative charge

Thermal stability vs ion polarisation

smaller cations will have greater polarizing power, so it is more likely for the anion to be broken down, so it will have a lower thermal stability

Enthalpy change of hydration

enthalpy of hydration decreases down the group, as radius increases and
charge density decreases

Change in lattice energy

lattice energy decreases down the group, as it is greater when ions are small and have a higher charge density

Group 2 sulfates vs hydroxides

Lattice energy decreases more in hydroxides
Enthalpy change of hydration decreases more in sulfates
Enthalpy of solution becomes more positive in sulfates, more negative in hydroxides
Solubility of sulfates decreases, while the solubility of hydroxides increases

Cleantha JC2G

2021-11-16 16:53:05 UTC

1. Factors affecting rate of polarisation:

• small cation -> higher positive charge

• large anion -> higher negative charge

- to get higher charge density -> having higher positive charge and smaller radius

- for cations, if yoh have more charge density, will be able to polarize the anion

2. Thermal Stability of Group 2 Carbonates and Nitrates

• when observing from a table, the one that requires more heat/energy, is the one that is more stable

• going down the group 2 carbonate, it is going to be more difficult to decompose which also means the thermal stability increases

• the atom with the smallest radius will be able to polarizer the carbonate ion

• distortion occurs as bonds between carbonate and oxygen weakens

(repeat from last time)

• lattice energy -> always negative

• enthalpy of solution -> can be both positive or negative

- if enthalpy is negative or very low positive value, substance is soluble

- if enthalpy is positive, it is insoluble

• enthalpy of hydration-> always negative

3. Solubility of Group 2 Sulfates and Hydroxides
• solubility of sulfates decreases down the group
• solubility of hydroxides increases down the group
- as it is the same group, it will have the same charge:

•if it is a smaller ion, it will have a greater enthalpy of hydration so it decreases down the group (for both sulfates and hydroxides)
• if it is a smaller ion, greater lattice energy so it decreases down the group (for both sulfates and hydroxides)

Dylan JC2G

2021-11-16 16:57:07 UTC

From today's lecture, I have learnt about:

Ion Polarisation

Positive charges on the cation may attract the electrons in the anion, resulting in distortion of the electron cloud
Ability to attract electrons and distort an anion is called the polarizing power of the cation

Factors that affect Ion Polarisation

small cation, so higher positive charge
anion is large, so having more negative charges

Thermal Stability of Nitrates and Carbonates

The thermal stability increases down the group, as going down the group, the ability to polarise decreases, as the cation size increases, so greater ionic radius and lower charge density. Since there is less ion polarisation, the ions become less distorted and the bonds are harder to break when decomposed.

Solubility of Sulfates

Down the group, the solubility of sulfates decreases, as both the lattice and hydration enthalpy of the sulfates become less negative but the decrease in the magnitude of hydration enthalpy is greater, though they are still exothermic.

Latt = hyd - sol

Hence, as the value of hyd becomes more endothermic, this must be balanced by a large increase in the enthalpy of solution. If sol is a large positive value, which is more endothermic, the compound is more likely to be insoluble.

Solubility of Hydroxides

The solubility of hydroxides increases down group 2. Going down the group, the enthalpy change of hydration and lattice energy of group 2 cations becomes less negative going down the group.

However, the lattice energy experiences a greater positive increase than the enthalpy change of hydration.

Sol = hydration - lattice

Therefore, the enthalpy of solution becomes more negative and hydroxides increase in solubility down the group.

I think overall I got an idea of the concept of what we had learnt so far, and I think with enough practice with past year questions, I'll be able to fully understand this chapter. As usual, it was a great lecture and easy to follow along.

Sharon JC2T

sharonchristiehalimm — 2021-11-16 17:08:52 UTC

Ion polarisation

Polarizing power : the ability to attract electrons and distort an anion
- Cation is the one who polarize anions

Factors affecting polarisation

Cation must have a high charge density (charge / radius). Charge density is inversely proportional to the radius. The bigger the charge density, the smaller the radius. [the charge is spread out over a smaller volume so the charge density is higher]
- Small cation
- Higher positive charge [more positive charge, higher charge density]
When radius is greater, the electrons will not hold tightly to the nucleus. Therefore, they are easier for the cations to distort an anion.
- Anion is large
- Anion having more negative charges

Thermal stability of group 2 carbonates and nitrates

Thermally stable : stable at high temperature and do not decompose easily

Explaining the trends using ion polarisation
- Thermal stability increase down group 2 [difficult to decompose]
- Going down the group, highest polarising power on cation is magnesium carbonate due to a smaller radius [able to polarise carbonate]
  - Due to ion polarisation in the carbonate ion, the C - O bond will weakened and broken down easily [decomposition happens]
  - Greater polarisation of carbonate ion → easier to weaken a C - O bond (in carbonate ion) → forming carbon dioxide and oxide [on heating]

Lattice energy, enthalpy of solution and enthalpy of hydration

Lattice energy [always negative]
Enthalpy of solution : [can be positive or negative]
- Soluble → enthalpy of solution (-) / small positive value
- Large positive enthalpy of collusion → insoluble
Enthalpy change of hydration : [always negative]
- More exothermic → smaller radius (same charge) and larger charge (same radius)

LET YOUR SOUL GO AND HIDE

Latt = hyd - sol

Change in hydration enthalpy down the group

If same charge → smaller cations → greater enthalpy of hydration → enthalpy of hydration decreases going down the group

Change in lattice energy down the group

If same charge → smaller ions → lattice energy greater → lattice energy decreases going down the group → inversely proportional to radius

SOL = HYD - LATT

Solubility of group 2 sulfates and hydroxides

Solubility of sulfates decreases down the group [hydration decreases more]
Solubility of hydroxides increases down the group [lattice energy decreases more]

LARGE POSITIVE VALUE OF SOL → insoluble
SMALL POSITIVE VALUE / NEGATIVE VALUE OF SOL → soluble

Nevan Kho

2021-11-16 17:34:51 UTC

Cation small, high positive charge

Anion large, high negative charge

Maximises polarisation due to high charge density and easily polarised anions

Thermal stability increase as go down group, polarisation decreases as charge density decrease

Sulfates lattice energy decrease by smaller increments, hydroxides hydration enthalpy decrease by smaller increments.

Sulfates: lattice energy is inversely proportional to sum of radii, sulfate has larger radii that decreases impact of increasing radius down group.
Hydroxides: hydration is separate equations. Hence size of anion does not matter, but lattice energy will matter more.

Earlene JC2G

2021-11-16 18:06:39 UTC

Ion Polarisation

polarising power refers to the ability of a cation to attract electrons and distort an anion

Factors Affecting Polarisation

charge density of cation
- cation must be small in size and be high in positive charge to have a higher charge density
polarisability of anion
- anion must be large in size (less attraction between nucleus and electrons) and be high in negative charge (greater attraction between negative and positive charges of the anion and cation respectively) to be more polarisable

Thermal Stability of Group 2 Carbonates and Nitrates

increasing thermal stability down the group
polarisation causes bonds to weaken and be broken easily
cations increase in size down the group, hence they decrease in polarising power, thus the compounds have increasing thermal stability down the group

Lattice Energy

always negative

Enthalpy Change of Solution

can be positive or negative
solubility of substance
- negative or small positive value - soluble
- large positive value - insoluble

Enthalpy Change of Hydration

always negative
becomes more negative when ionic radius is smaller for the same charge
becomes more negative when charge is larger for the same ionic radius

Enthalpy Change of Hydration = Enthalpy Change of Solution + Lattice Energy

Solubility of Group 2 Sulfates and Hydroxides

sulfates are decreasingly soluble down the group
hydroxides are increasingly soluble down the group
for ions of the same charge
- enthaply change of hydration decreases down the group
- lattice energy decreases down the group
lattice energy of sulfates decrease by a smaller value than that of hydroxides
enthalpy change of hydration of sulfates decrease by a larger value than that of hydroxides
enthalpy change of solution becomes more positive for sulfates while for hydroxides, it becomes more negative

Group 2 Submission
https://docs.google.com/document/d/14zk9hr495Hezcoa5DMPWLuINgPSw-nY7rN1x_mMH7No/edit?usp=drivesdk

michelle jc2grace

2021-11-17 00:20:28 UTC

factors that affect ion polarisation:

charge density

size of the cation or anion

cation has higher polarising power if:

higher positive charge

smaller cation

anion is more easily polarised if:

higher negative charge

larger anion

ion polarisation of thermal stability of both Group 2 carbonates and nitrates:

The higher the polarisation power the more easily the compounds get thermally decomposed. Going down group 2, the size of the cation increases so the polarising power of cation decreases. Hence, the thermal stability for carbonates and nitrates going down group 2 increases.

solubility of sulfates and hydroxides down the group 2:

Going down the group, the solubility of sulfates decreases while the solubility of hydroxides increases.

lattice energy, enthalpy of hydration and enthalpy of solution with the trend of solubility of sulfates down Group 2:

lattice energy of sulfate decreases (by smaller values) down the group

enthalpy change of hydration decreases (by larger values) down the group

enthalpy of solution gets more endothermic down the group

enthalpy of solution becomes less negative down the group, hence the sulfates become increasingly insoluble down the group

lattice energy, enthalpy of hydration and enthalpy of solution with the trend of solubility of hydroxides down Group 2:

lattice energy of hydroxides decreases (by larger values) down the group

enthalpy change of hydration decreases (by smaller values) down the group

enthalpy of solution gets more exothermic down the group

enthalpy of solution becomes more negative down the group, hence the hydroxides become increasingly soluble down the group

the lesson was clear as usual, very detailed and is understandable

Catherine

2021-11-17 01:52:46 UTC

learnt:

Ion polarization
Factors affecting ion polarization
Thermal stability of group 2 carbonates and nitrates increase down the group (ion polarizing power decrease)
Effect of ion polarization on solubility of sulfates and hydroxides
Difference in graph of sulfates and hydroxides

Audrey

2021-11-17 14:20:14 UTC

- ion polarization (charge density decreases, polarising effect decreases down the group)
- the more polarized the anion is, the less hear required to thermally decompose
- solubility of hydroxide increases down the group, decrease in lattice energy > decrease in enthalpy of hydration, enthalpy of solution more exothermic
- solubility of sulfates decreases down the group, decrease in lattice energy < decrease in enthalpy of hydration, enthalpy of solution more endothermic
- thermal decomposition of sulfates and hydroxides

Ryan JC2Truth

2021-11-18 07:09:59 UTC

Learnt:

-Ion polarization
- Different factors that affects polarization:
1. The size of the cation
2. The amount of positve charge (Higher amount of positive charge will cause higher charge density that increases polarity)
3. The size of anion
4. The amount of negative charge
- Thermal stability of nitrates and carbonates increases down the group, the ability to polarize would decrease down the group due to larger cation size, so there is the lower charge density
- The solubility of sulfate decreases down the group (Decrease in lattice energy > Decrease in enthalpy of hydration)
- The solubility of hydroxide increases down the group ( Decrease in lattice energy> Decrease in enthalpy of hydration)
- Latt = hyd - sol (Let your soul go and hide)