Bonding And Structure

Question 1

Giant ionic lattices have high or low melting and boiling point? Explain your answer.

Answer 1

They have high melting and boiling point because a large amount of energy is required to overcome the electrostatic bonds.

Question 2

In what type of solvents do ionic lattices dissolve?

Answer 2

Polar solvents

Question 3

Why are ionic compounds soluble in water?

Answer 3

Water has a polar bond. Hydrogen atoms have a + charge and oxygen atoms have a - charge. These charges are able to attract charged ions.

Question 4

What is average bond enthalpy?

Answer 4

Measure of average energy needed to break the bond.

Question 5

What is a dative covalent bond?

Answer 5

A bond where both of the shared electrons are supplied by one atom.

Question 6

How are oxonium ions formed?

Answer 6

Formed when acid is added to water, H30+

Question 7

What does expansion of the octet mean?

Answer 7

When a bonded atom has more that 8 electrons in the outer shell

Question 8

What are the types of covalent structure?

Answer 8

• simple molecular lattice
• giant covalent lattice

Question 9

Describe the bonding in simple molecular structures.

Answer 9

Atoms within the same molecule are held together by strong covalent bonds and different molecules are held by weak intermolecular forces.

Question 10

Simple molecular structures dissolve in what type of solvent?

Answer 10

Non polar solvents

Question 11

Give examples of giant covalent structures

Answer 11

• diamond
• graphite
• silicon dioxide

Question 12

List some properties of giant covalent structures? (3)

Answer 12

• high melting point and boiling point
• non conductors of electricity except graphite
• insoluble in polar and non polar solvents

Question 13

Draw and describe the structure of a diamond.

Answer 13

3D tetrahedral structure of C atoms, with each C atom bonded to four others.

Question 14

What does the shape of a molecule depend on?

Answer 14

NO. Electron pairs in outer shell
NO, bonded pairs and lone pairs

Question 15

What is the shape and bond angle in a shape with 5 bonded pairs and 0 lone pairs?

Answer 15

Trigonal bipyramid
90 degrees and 120 degrees

Question 16

What is the shape and bond angle in a shape with 6 bonded pairs and 0 lone pairs?

Answer 16

Octahedral
90

Question 17

By how many degrees does each lone pair reduce the bond angle?

Answer 17

2.5 degrees

Question 18

Define electronegativity

Answer 18

The ability of an atom to attract the pair of electrons in a covalent bond

Question 19

What is the most electronegative element?

Answer 19

Fluorine

Question 20

Why is H2O polar, whereas CO2 is non polar?

Answer 20

CO2 is a symmetrical molecule, so there is no overall dipole

Question 21

What is meant by intermolecular force?

Answer 21

Attractive force between neighbouring molecules

Question 22

Describe london forces.

Answer 22

• london forces are caused by random movements of electrons
• this leads to instantaneous dipoles
• instantaneous dipole induces a dipole in nearby molecules
• induced dipoles attract one another

Question 23

Does boiling point increase or decrease down the noble gas group? Why?

Answer 23

Boiling point increases because the no. electrons increases and therefore the strength of london forces also increases

Question 24

Why is ice less dense that liquid water?

Answer 24

In ice the water molecules are arranged in an orderly pattern. It has an open lattice with hydrogen bonds
In water, the lattice is collapsed and the molecules are closer together

Question 25

Why does water have a high melting/boiling point that expected?

Answer 25

Hydrogen bonds are stronger than other intermolecular forces so extra strength is required to overcome the forces.