Ionic and Covalent Compounds

Question 1

Compared with covalent compounds, ionic compounds generally have:

Accepted Answer

Higher melting points — Strong ionic bonds throughout a giant lattice need much energy to break, giving high melting points.

Question 2

An ionic compound conducts electricity when:

Accepted Answer

It is molten or dissolved in water — Only when ions are free to move (molten or aqueous) can they carry current.

Question 3

Which type of compound is usually soluble in organic solvents but not water?

Accepted Answer

Covalent compounds — Molecular covalent compounds tend to dissolve in organic (non-polar) solvents rather than water.

Question 4

Why does solid sodium chloride NOT conduct electricity?

Accepted Answer

Its ions are fixed in the lattice and cannot move — In the solid, ions are locked in position, so there are no free charge carriers.

Question 5

A substance has a low melting point and does not conduct electricity in any state. It is most likely:

Accepted Answer

Covalent (molecular) — Low melting point and no conductivity are typical of simple covalent molecular substances.

Question 6

Which of these is generally true of covalent compounds at room temperature?

Accepted Answer

Often liquids or gases — Weak intermolecular forces mean many covalent compounds are liquids or gases at room temperature.

Question 7

Substance Y melts at 780 °C and its molten form conducts electricity. Y is most likely:

Accepted Answer

An ionic compound — High melting point plus conduction when molten indicates a giant ionic structure.

Question 8

Ionic compounds are usually soluble in:

Accepted Answer

Water — Polar water molecules can surround and separate ions, so ionic compounds usually dissolve in water.

Question 9

The strong forces holding an ionic lattice together are:

Accepted Answer

Electrostatic attractions between ions — A giant ionic lattice is held by strong electrostatic ionic bonds between oppositely charged ions.

Question 10

Which pairing of property and compound type is INCORRECT?

Accepted Answer

Covalent – conducts when solid — Simple covalent compounds do not conduct in any state; the other three pairings are correct.

Property	Ionic	Covalent
Melting/boiling point	High	Low
State at room temp.	Solid	Often liquid or gas
Conducts as solid	No	No
Conducts molten/aqueous	Yes	No
Solubility in water	Usually soluble	Usually insoluble
Solubility in organic solvent	Insoluble	Usually soluble