Chapter 12: Water as a Solvent Flashcards
What is water often described as ..
“universal solvent”
WhAT IS water an excellent solvent for?
Many ionic and polar substances.
What does a readily dissolved substance depend on?
The polar nature of the water molecules
The nature of substance that dissolves in it.
What happens to molecular compounds mixed with water?
Some dissolve: Some Ionic compounds
Some are insoluble: Oil
What are the key factors of substances mixing with water?
- Biological
- Domestic
- Industrial situations
What is a precipitation reaction?
Two solutions reacts and produce an insoluble product
Solute meaning?
Substance that is dissolved
Solvent meaning?
Liquid that the solute is dissolved in
Together was does Solute & Solvent form?
A homogenous solution
uniform composition and properties throughout the whole solution.
Aqueous solution meaning?
Solvent is water..thats what the solution is called
Solubility meaning?
Extent to which SOLUTE can dissolve in a solvent.
What is Solubility also determined by?
Polar or non-polar nature of the solute and the solvent.
‘like dissolve like’ according to chemist mean
Strongly polar and ionic solutes tend to dissolve in polar solvents,
and non-polar solutes tend to dissolve in non-polar solvents
Process of dissolving also depend on..
Strength of the attraction or bonds between the solute particles, and
the attraction between the solvent particles and the new bonds that form between the solute and the solvent.
What is strength related to..?
Size of the energy required to break these bonds, compared to the energy released when the new attractions or bonds are formed.
Why is water an effective solvent?
Due to its polarity and ability to form hydrogen bonds.
What is energy used for?
Energy is required to break bonds
Energy is released when new bonds form
what happens when ionic compounds dissolve in water.
Cations attract to ned end of water and anions attract pos end of water.
If strong enough it breaks bonds between cation and anions,
compound dissolves
when ion dissolves in water its called
described as hydrated (contain water molecules within structure )
interaction between water ( any polar ) molecule and ion is
ion-dipole attraction
dissociation meaning
ions seperate when an ionic compound dissolves in a solvent
ions are surrounded by water molecules and cannot recombine
when ionic substances dissolve in water..
they dissociate (ions separates )
What if strength of ions are very strong?
The water molecules are unable to seperate the ions and the salt is insoluble
insoluble meaning
will NOT DISSOLVE
molecular meaning
group of atoms bonded together covalently
many do not dissolve in water
What is it called when molecules dissolve in water
Are highly polar, and described as dipoles
diff between polar and non-polar
non-polar: even distribution of charge
polar: uneven distribution of charge due to differences in electronegativity of the atoms
Polar molecules will dissolve in water cause they either (2)..
- Form ions in water
2. Form hydrogen bonds with water
Molecular compounds that ionise in water example
Why does it happen
HCl = hydrogen chloride ( highly polar )
Hydrogen ions combine with water = hydronium ions H3O+
Aqueous solution = hydrochloric acid
Attraction of the polar water molecule increase polarity of H-Cl bond … neg attracts H and so and pulls it away.
H atom covalently bonds with water ( aqueous )
Cl becomes aqueous ( the anion dissolves ) ( aqueous )
Both ions are hydrated and dorm ion-dipole interactions
Ionisation meaning
Process polar molecules compounds form ions when dissolved in water
What does highly polar molecular substances usually do?
They ionise in water when they dissolve.
What are the other molecular compounds that are soluble in water?
Molecules usually having hydrogen atom bonded to one F, O or N.. they dissolve by forming hydrogen bonding with water.
example: NH3 ammonia
Simplify four molecular compounds that dissolve in water.
- Ions : cation and anion
- Ionisation of molecular ( ion and hydrogen )
UNLESS THE BOND IS TOO STRONG LIKE AgCl - Hydrogen bond with F, O , N
- Alcohol molecules
Why are alcohol molecules soluble?
Form hydrogen bonding such AS with CH3OH
CH3-OH : methanol
the OH is highly polar + water = hydrogen bonding
however hydrogen bonding does not occur with CH3 due to small electronegativity / not very polar
so bond is like CH3-OH-0HH
Interesting about water & alcohol molecules interaction?
They take up less volume due to rearrangement of the molecules.
The volume of combined liquids is less than the sum of individual volumes.
Miscible meaning?
Two liquids able to be mixed and form a solution