16 Aqueous Solution Flashcards
Water as a solvent
Most molecular substances are insoluble in water but a good solvent for some polar molecular compounds.
2 main reasons it’s a good solvent:
By forming hydrogen bonds with water
By ionising to form hydrated ions.
How does ethanol dissolve in water?
Water molecules break
Ethanol molecules break
Ethanol molecules and water molecules form an aqueous solution
Examples of soluble compounds in water
Ammonia, sucrose (sugar) fructose glucose.
The more polar they are, the more likely it is to dissolve.
Molecules that ionise in water
Highly polar molecular compounds form ions when dissolved.
Eg HCL when added to water, the hydrogen atom has a strong attraction to oxygen causing the covalent bond to break.
Ions form CL H3O+ become hydrated, held together ion-dipole attractions
What chemicals ionise in water
Nitric acid sulphuric acid and ethanoic acid dissolve in water by ionising. Ammonia ionises to form ammonium
The polar water molecules r attracted positive and negative ions of ionic solute. Ion dipole dipole forces hold molecules to the ions. These ions with water molecules attracted to them are called complex ions.
Electrostatic attraction attracts negative ions of NACL in a lattice and the hydrogen atoms in polar water molecules.
Electrostatic attraction also occurs between positive ions in lattice and the oxygen atoms in the water.
Why dont Insoluble ions dissolve in water
because energy required to seperate ions from lattice is greater than the energy released when ions r hydrated.
What are soluble salts
SNAPE
Sodium
Nitrate
Ammonium
Potassium
Ethanoate
Supersaturated solution
Holds more solute than theoretically possible at that temperature.
Saturated solution
Holds maximum amount of solute possible
Unsaturated solution
Could hold more solute
Precipitation reactions are good for:
To remove minerals from drinking water and
Spectator ions are
Ions that remain uncharged in a solution when 2 ionic compounds are mixed and a precipitate form
How do precipitates get their colour
Determined by the colour of their ions. Colourless ions form white precipitate.
How do u describe observations on precipitation
- colour of reactants and products
- give reasoning why
Ionic equations
Includes only atoms which undergo a chemical change during reactions and therefore are usually written as ions. Do not include spectator ions
Full equation
- balanced
- states of matter
- all chemicals are included
Molarity
Moles/litre
