0620/11/M/J/19/ no links please How could crystals of a pure salt be prepared from dilute
sulfuric acid?
A add an excess of aqueous sodium hydroxide, filter, evaporate
the filtrate to crystallisation point
B add an excess of copper (II) carbonate, filter, evaporate the
insoluble
filtrate to dryness
Copper sulfate.
C add an excess of copper metal, filter, evaporate the filtrate to
crystallisation point
Soluble
D add an excess of zinc oxide, filter, evaporate the filtrate to
crystallisation point
insoluble​

intermolecular forces are the forces between molecules or particles.

there are two kinds of van der waals forces: weak london dispersion forces and stronger dipole-dipole forces.

in molecule of water there are dipole-dipole forces between negatively charged oxygen from one molecule of water and positively charger hydrogen of another molecule of water.

hydrogen bond is an electrostatic attraction between two polar groups that occurs when a hydrogen atom (h), covalently bound to a highly electronegative atom such as flourine (f), oxygen (o) and nitrogen (n) atoms.