Solvents Flashcards
strength of london dispersion forces
weak intermolecular force
strength of dipole-dipole forces
intermediate strength
strength of hydrogen bonding
strong interaction
solute
This is the substance that gets
dissolved. It can be a solid, liquid, or even a gas. Think of it as the “guest” in the mixture.
A substance dissolved in a solvent to form a solution
solvent
This is the substance that does the
dissolving. It’s usually present in a larger amount compared to the solute and acts as the “host” in the mixture, providing the medium for dissolving
the solute.
The dissolving medium of a solution
polarity of hydrocarbons
In general hydrocarbons are non polar
Aprotic solvent definition
incapable of donating a proton
In general compounds containing ketones (C=O) and ethers
(C-O-C) are polar ———- Dipole-Dipole interactions
Organic Compounds
Containing-Ketones,
Aldehydes and Ethers
From the electronegativity table C-O bond is polar covalent bond
Polar protic solvents tend to have high dielectric constants and high dipole moments.
Furthermore, since they possess O-H or N-H bonds, they can also participate in hydrogen bonding.
Polar compounds dissolve in Polar compounds and
Non-Polar compounds dissolve in Non-polar compounds
- Solute molecules are separated from each other.
Solute–Solute attractions resist this.
- Solvent molecules are separated from each other.
Solvent–Solvent attractions resist this.
- Solute and solvent molecules mix with each other.
Solute–Solvent attractions assist this.
Each one of these has a particular energy called (H) in this case it is
Heat energy (called Enthalpy) a change in heat energy is (triangle symbol)H
Molecular substances will dissolve in each other if:
- H initial and H final are of similar energy H
- Both solute–solute attractions and solvent–solvent attractions are weak so
that there is little resistance to the tendency to mix - The solute–solvent attractions are sufficiently strong to overcome the
resistance to mixing due to solute–solute and solvent–solvent attractions
What other factors are helping in the formation of one substance dissolving
in another?
Energy systems have a tendency to increase their Entropy (S).
Entropy S is a measure of disorder
The universe is moving towards greater disorder or larger Entropy
Applied to our system the solute and solvent has a natural tendency to mix
or move towards greater disorder
The universe is moving towards greater disorder or larger Entropy
Applied to our system the solute and solvent has a natural tendency to mix
or move towards greater disorder
The same reason why N2 and O2 do not move towards more order by separating
out in the room. Probability of disorder or the permutations are larger
Miscible
If substances are soluble in one another
Are Ethanol and Water miscible?
- Ethanol and Water are miscible because, They form hydrogen bonds between each other
Are Hexane and Octane miscible?
- Hexane and Octane are miscible because,
The have form weak London dispersion forces between each other and begin with only
weak Hexane-Hexane and Octane-Octane dispersion forces
- Hexane and Water are immiscible because:
The hydrogen bonds in water prevent the mixing
The hexane-hexane interaction has only weak London dispersion force and overall the mixed system (if it
existed) would have far greater energy than the combined Hexane-Hexane and Water-Water systems
As the non-polar end of any alcohol is increased so does its chances of being soluble in a nonpolar molecule. And less chance of being soluble in water
oxidise reaction
acid-base reaction
chemical change macrosopic
a change in colour
* a change in temperature
* the evolution of heat
* a change of phase (e.g.
precipitation of a solid out of a
solution)
* the emission of light.
