Factors affecting solubility

Question 1

What is the trend in solubility as you go down group 2 hydroxides?

Answer 1

Group 2 hydroxides become increasingly soluble as you go down the group

Question 2

What is the trend in solubility as you go down group 2 sulphates?

Answer 2

Group 2 sulphates become less soluble as you go down the group

Question 3

What is the trend in solubility as you go down group 2 carbonates?

Answer 3

Group 2 carbonates become less soluble as you go down the group

Question 4

What solubility is calcium sulfate classed as?

Answer 4

Slightly soluble

Question 5

What solubility is strontium sulfate classed as?

Answer 5

Insoluble

Question 6

What solubility is barium sulfate classed as?

Answer 6

Insoluble

Question 7

What solubility is magnesium sulfate classed as?

Answer 7

Soluble

Question 8

Why are group 2 oxides classed as basic oxides?

Answer 8

They react with water to form alkalis

Question 9

Why does HF have a lower boiling temperature than water, despite the hydrogen bonds being stronger?

Answer 9

• Water forms more hydrogen bonds per molecule than HF

- Not all of the hydrogen bonds in HF are broken on vaporisation

Question 10

In order for a substance to dissolve, what two conditions must be met?

Answer 10

• The solute particles must be separated from each other, and then surrounded by solvent particles
• The forces of attraction between the solute and solvent particles must be stronger than the solute-solute and solvent-solvent forces

Question 11

Why does NaCl dissolve in water?

Answer 11

• The energy required to separate the ions is supplied by the hydration of the ions
• The delta - oxygens are sufficiently attracted to the Na+
• The delta + hydrogens are sufficiently attracted to the Cl-

Question 12

What is the interaction between the ions in NaCl and water known as?

Answer 12

Ion-dipole interactions

Question 13

What is the structure of dissolved sodium and chloride ions?

Answer 13

They will be surrounded by water molecules, with the delta - oxygens facing towards it. This is the same for the Cl- ions, but the delta + hydrogens will be facing it.

Question 14

Are alcohols soluble in water and why?

Answer 14

They are soluble, as hydrogen bonds form between the lone pair of the OH group and the delta + hydrogen.
This is the same with carboxylic acids, carbonyls and other compounds

Question 15

What is the trend in solubility as chain length increases and why?

Answer 15

As the hydrocarbon chain length increases, solubility decreases. This is because the increasing level of London forces interrupts the formation of hydrogen bonds with water

Question 16

Why are some compounds (like alkanes) insoluble in water?

Answer 16

The attraction between the compounds molecules and water molecules is not sufficiently strong enough to replace the hydrogen bonded system already present between the water molecules

Question 17

What is the rule of thumb for solubility?

Answer 17

Like dissolves like; polar substances tend to dissolve in polar solvents and vice versa

Question 18

What is an example of non-polar dissolving in non-polar?

Answer 18

Br2 dissolves in cyclohexane (both are non-polar)