The Ionic Model · Paper 1 — Free Chemistry HL Practice Questions

Sodium chloride and magnesium oxide both adopt the rock-salt crystal lattice structure. The melting point of NaCl is 801 °C, while that of MgO is 2852 °C. Which statement best explains why MgO has a significantly higher melting point?

A solid sample of sodium chloride does not conduct electricity, but an aqueous solution of sodium chloride does. Which statement correctly explains both observations?

A white crystalline solid melts at $801\ ^\circ\text{C}$ and boils at $1413\ ^\circ\text{C}$. The molten liquid does not conduct electricity, but an aqueous solution of the solid does conduct electricity. Which type of bonding is present in the solid?

Lithium fluoride (LiF), sodium chloride (NaCl), and potassium bromide (KBr) all adopt the same ionic crystal structure and carry ions of charge $\pm 1$. Their melting points are: LiF $= 845\ ^\circ\text{C}$, NaCl $= 801\ ^\circ\text{C}$, KBr $= 734\ ^\circ\text{C}$. Which statement correctly explains this trend?