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how do Aqueous solutions form
form when a solid, liquid or gas (solute)dissolve in water (solvent)
Aqueous solutions
Properties
solute particles too small to be seen and can vary in amount
solvent + solute cannot be seen individually
Why does water have low density as a solid
This is due to it forming a lattice as a solid.
having up to 4 bonds
Dissolution or not
Polar-polar
dissolution
Dissolution or not
non polar-non polat
dissolution
Dissolution or not
polar-non polar
no dissolution
whats dissolution
The process of dissolving substances
universal solvents
like water, can dissolve a wide range of substances due to their polar nature. resulting in separation of various solutes
what happens during dissolution
the solvent particles separate
the solute particles separate
solute and solvent particles are attracted to each other
why are most molecular substances insoluble in water
due to them having weak IMF
What are 2 ways molecular substances can become soluble
H-bonds and ionisation
Solubility via H-bonds
Dissolution occurs and it requires a lot of energy to break off
What happens when a substance what forms H-bonds dissolves in Water
The H-bonds break apart and form new bonds with the water
solubility with ionisation
molecules having strong covalent bonds that are so polar they break in water=ions
eg. HCL ionises into H and Cl when dissolved in water
Dissolution of ionic lattice
What happens to the lattice when it dissolves
When it dissolves the positive end of the water molecules become attracted to the negative end of the substances and vice versa
how can the outer layer of the lattice be removed
If dipole forces between water and ions is strong enough it'll break These free ions= hydrated
whats dissociation
the process of a solid ionic compound dissolving in water to form hydrated ions
What can break the lattice
ion dipole forces between one ion and several H20s. These dipole attractions form new bonds between H20 and ions
properties of water
High MP/BP
Due to H-bonds a large amount of energy is needed to break it and as the molecules size increase so does its dispersion forces resulting in the need of higher BP
properties of water
water as a solid
it forms a crystal lattice and is less dense than liquid allowing it to float
When does crystallization occur
occurs when an unsaturated solution becomes saturated
what are 2 ways crystallisation occurs
Evaporation and cooling
define how evaporation leads to crystallisation
When a solvent evaporates, the solubility of the solution decreases causing the solute to become a solid
define how cooling leads to crystallisation
If an unsaturated solution is cooled, it will eventually reach saturation if you keep cooling it, it becomes supersaturated= crystals
Crystal Growth
How is a crystals size and shape determined by Rate of cooling
slow cooling=large crystals as they have time to grow,
Fast cooling= smaller crystalls
Crystal Growth
How is a crystals size and shape determined by Rate of solvent evaporation
Fast evaporation = small crystals
Slow evaporation = large crystals
Crystal Growth
How is a crystals size and shape determined by Nucleation:
Crystallisation occurs quicker if a seed crystal or ‘nucleus’ is added
Crystal Growth
How is a crystals size and shape determined by Nature of Compound:
by the molecular structure, bonding type and strength of bonding, growth conditions,
Whats solubility
The maximum amount of soulte that can be dissolved in a solvent at a certain temperature
When dissolving solutes into solvents what 3 types of solutions form
Saturated solutions: no more solute dissolves
Unsaturated solution: more solute dissolves
Supersaturated: Becomes unstable and crystals form
Solubility of liquids and gases
Liquids don’t show solubility trends
Gases tend to be less soluble in water at high temp
How does a precipitation reaction occur
If ions in a solution combine to form an insoluable compound
How to predict precipitation reactions
Identify the ionic compund
swap the anions
see if the new ionic compound goes against the solubility table
identify the ppt if any
grams per litre, g/l formula
Mass of solute (g)
-----------------
V of solvent (L)
parts per million ppm formula
mass of solute (mg)
-------------------
mass of solvent in (kg)
percentage composition
mass of solute (g)
----------------- x 100
mass of solvent (g)
Note
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