Ionic Compounds Flashcards
Comment on the physical state of ionic compounds?
Ionic compounds are hard, crystalline solids. The crystals have flat sides and regular shapes. The ions are arranged in straight rows form a large structure with flat sides. the ions are held in place by strong ionic bonds, which make the crystals hard.
Comment on the melting and boiling points of ionic compounds.
Very high
Why do ionic compounds have high melting and boiling points?
For an ionic solid to melt, the electrostatic attractions between the ions need to be
overcome. Since these are very strong, high temperatures are required.
Comment on the volatility of ionic compounds.
Because of the strong forces holding the ions together, an ionic compound cannot evaporate easily. Hence salt has no smell.
Can solid ionic compounds conduct electricity?
No
Why do ionic compounds conduct electricity when molten?
When ionic solids are molten, the electrostatic forces between the ions no longer
hold them in place. Thus, they are free to move in the liquid if a potential difference is
applied to electrodes placed in the sample.
Positive ions are free to move to the negative
electrode and negative ions move to the
positive electrode. This completes the circuit
and as such electricity can be conducted
through the liquid.
Why are ionic compounds brittle?
The forces between the ions are very strong and hold them in their specific positions.
If, however, a force is applied that shifts an ion out of position, repulsion occurs and
the lattice falls apart – it shatters.
Comment on the solubility of ionic compounds.
Soluble in water but insoluble in non-aqueous solvents.
Why are ionic compounds soluble in water?
This is because there is an attraction between the ions and the water molecules, causing the ions to separate and go into the solution.
Why are ionic compounds insoluble in non-aqueous solvents?
This is because there is no attraction between the ions and the molecules of non-aqueous solvents and so the solid doesn’t dissolve.
Why is there no current in the distilled water?
Distilled water is pure H2O. Pure water is very resistant to conducting
electricity. Pure water only contains neutral water molecules that are bonded by strong
covalent bonds (intramolecular bonds). These neutral molecules do not have any charge
and are therefore unable to conduct electricity.
Why is there current in the saltwater?
Saltwater has salt in it: NaCl (ionically bonded compound). When dissolved in water, the
salt (NaCl) dissociates to form ions of Na+ and Clthat can move freely through the water
carrying a charge, and thus conduct electricity. Note that not all ionic substances are soluble,
but NaCl is highly soluble in water.
