8.3: The Dissolving Process

Question 1

there are forces of attraction between ______ and ___________ particles

Answer 1

solute; solvent

Question 2

when the forces of attraction between different particles in a mixture are _______ than the forces of attraction between like particles in the mixture, dissolving occurs and a ______ forms

Answer 2

stronger; solution

Question 3

the strength of the attraction influences the ______ or the amount of a solute that dissolves in a solvent

Answer 3

solubility

Question 4

what happens at a molecular level when substances dissolve in step 1

Answer 4

forces between the particles in the solute are broken

requires energy

in an ionic compound, the forces between ions must be broken

in a covalent compound, forces between molecules must be broken

Question 5

what happens at a molecular level when substances dissolve in step 2

Answer 5

some intermolecular forces between solvent molecules must be broken

this step requires more energy

Question 6

what happens at a molecular level when substances dissolve in step 3

Answer 6

attraction between molecules of the solute and solvent (dissolving)

this step gives off energy

Question 7

dissolving of ionic compounds

imagine a crystal of sodium chloride dropped into water…

the sodium chloride is a crystal lattice with its ions held together by electrostatic forces

what happens…

Answer 7

the water will surround the crystal lattice with the negative oxygen atom of the water molecule being attracted to the positive sodium ions and the positive hydrogen atoms of the water molecule being attracted to the negative chloride ion

this attraction is stronger than the electrostatic forces between the ions so the

CRYSTAL LATTICE GETS PULLED APART AND THE
SALT DISSOLVES

Question 8

the ions become __________ which means they are surrounded by water molecules

Answer 8

hydrated

Question 9

these hydrated ions can move through the solution and conduct electricity which means the solution is now an __________

the reaction is called a ______________

Answer 9

electrolyte; dissociation reaction

Question 10

miscible

Answer 10

describes liquids that mix with each other in all proportions to form a solution

Question 11

immiscible

Answer 11

unable to mix to form a solution

Question 12

hydrogen bonding between ethanol
and water

once dissolved the alcohol/water molecule is
overall ______ so the solution will ____ conduct
electricity and is a _________

Answer 12

neutral; not; non-electrolyte

Question 13

ethanol is miscible in water, meaning…

Answer 13

it can mix to form a solution

Question 14

why does oil remain on the surface of water

Answer 14

oil is a mixture of hydrocarbons, hence why it remains on the surface of water (because it does not dissolve and is less dense than water)

Question 15

a non-polar solute will dissolve in a…

Answer 15

non-polar solvent

Question 16

a polar solute will dissolve in a …

Answer 16

polar solvent

Question 17

a non-polar solute will ____ generally dissolve in a polar solvent (or vice versa), since the solute-solvent attractions are ______ than the attractions between solute particles or solvent particles

Answer 17

not; weaker

Question 18

What attractions must be overcome before a solute can dissolve in a solvent?

Answer 18

The attractions between solute and solvent must be great enough to overcome the attractions
between solute–solute and solvent–solvent for a solute to dissolve in a solvent.

Question 19

Why is water capable of dissolving sodium chloride but hexane, C6H14, is not?

Answer 19

Water is capable of dissolving sodium chloride because water is polar.

As water molecules approach a crystal of sodium chloride, they re-orient themselves so that the negative end of the molecule is attracted to the positively charged sodium ion and the positive end of the molecule is attracted to the negatively charged chloride ion.

Sodium chloride will not dissolve in hexane
because hexane is a non-polar molecule.

Question 20

Why is hydration a necessary part of dissolving?

Answer 20

Hydration is a necessary part of dissolving because it helps stabilize the ions in the solution, which prevents them from attracting each other.

Question 21

Explain what is meant by the expression “like dissolves like.”

Answer 21

The expression “like dissolves like” means that solutes dissolve in solvents of similar polarity.

Therefore, polar solutes dissolve in polar solvents and non-polar solutes dissolve in non-polar
solvents.

Question 22

identify one factor that affects the
solubility of alcohols in water

Answer 22

the factor that affects the solubility of alcohols in water is the number of carbon chains

Alcohols with three carbon chains or less are miscible

As the number of carbon chains increases above three, the solubility decreases.