Giant ionic structures
2 marks · HardState and explain whether potassium iodide (KI) has a high or low melting point. Refer to its structure in your answer.
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
Potassium iodide has a high melting point because it is a giant ionic compound. Strong electrostatic forces hold the ions together which require a lot of energy to overcome.
Also accept: High melting point due to giant ionic lattice and strong forces between oppositely charged ions.; KI has a high melting point because strong electrostatic attraction between K^+ and I^- ions requires much energy to break.
Common mistakes: Not mentioning strong forces.; Not referring to the lattice structure.
Show mark scheme and worked solution
Marking points
B1 · 1 mark · States KI has a high melting point.
M1 · 1 mark · Links high melting point to (giant) ionic lattice structure and/or strong electrostatic forces between ions.
Worked solution
Potassium iodide has a high melting point because it has a giant ionic lattice structure. The strong electrostatic forces between the oppositely charged ions require a large amount of energy to break.