Why things conduct electricity
4 marks · NormalState the type of bonding found in magnesium chloride.
Explain whether magnesium chloride conducts electricity when solid and when dissolved in water.
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
Show answer
(a) Ionic
(b) Solid magnesium chloride does not conduct electricity because ions are fixed in the lattice and cannot move. When dissolved in water, the ions are free to move so the solution conducts electricity.
Common mistakes: Confusing electrons with ions; Incorrectly stating both forms conduct
Show mark scheme and worked solution
Marking points
B1 (a) · 1 mark · Correctly identifies ionic bonding in magnesium chloride.
M1 (b) · 1 mark · States that solid MgCl2 does not conduct since ions are not free to move.
M2 (b) · 1 mark · States that dissolved MgCl2 conducts because ions are free to move.
A1 (b) · 1 mark · Makes a correct link between movement of ions and conduction in each state.
Worked solution
a) Magnesium chloride has ionic bonding.
b) Solid magnesium chloride does not conduct electricity because the ions are held in a fixed lattice and cannot move.
When magnesium chloride is dissolved in water, the ions are free to move so the solution can conduct electricity.