General Revision - Summer 2017

Question 1

What is a dative covalent bond?

Answer 1

A bond where one atom gives both the electrons in bond

Question 2

What is electronegativity?

Answer 2

Power of an atom to attract the electron density in a covalent bond

Question 3

What are three factors that influence electronegativity?

Answer 3

• Nuclear charge
• Atomic/ionic radius
• Electron shielding

Question 4

Explain why H20 is polar, but CO2 is non-polar.

Answer 4

• Bonds containing oxygen are polar
• CO2 is symmetrical
• Symmetrical shape of CO2 cancels the dipole

Question 5

What are the three key factors of the electron repulsion theory?

Answer 5

• Electron pairs repel each other
• Pairs take specific positions in order to repel each other
• Results in specific shapes of molecules and ions

Question 6

Why is ice less dense than water?

Answer 6

• Water molecules arranged into a fixed pattern
• Open lattice
• Hydrogen molecules hold water molecules apart with H bonds
• Allowing ice to be less dense than water

Question 7

What are the three types of intermolecular forces?

Answer 7

• Van der Waals/London forces
• Dipole-dipole forces
• Hydrogen bonding

Question 8

What are Van der Waals forces caused by?

Answer 8

Caused by random movement of electrons

Question 9

What do Van der Waals forces cause?

Answer 9

• causes temporary dipole

- temporary dipole induces further temporary dipoles to nearby atoms

Question 10

What do dipole-dipole forces act between?

Answer 10

Act between molecules with permanent dipoles

Question 11

Explain the trend in boiling points of the hydrogen halides from HCl to HI.

Answer 11

• Van der Waals forces of attraction
• Increase with increasing size of hydrogen halide
• Increase with increasing size of electron cloud

Question 12

How is a cation formed?

Answer 12

Formed through loss of electron

Question 13

How is an anion formed?

Answer 13

Formed through gain of electron

Question 14

Why does the polarising power of a cation depend on the ionic radius of an ion?

Answer 14

• Smaller radius = more polarising cation

- Positive charge of nucleus felt more strongly

Question 15

Why does the polarising power of a cation depend on charge on an ion?

Answer 15

• Larger charge = more polarising

- Stronger attraction for outer electron

Question 16

Why does the polarising power of an anion depend on the ionic radius?

Answer 16

-Larger ionic radius = electrons in outer shell held less tightly

Question 17

What is the key feature of a polar bond?

Answer 17

• Uneven distribution of electrons

- Bond having negative and positive end

Question 18

Why is water a good solvent for ionic compounds?

Answer 18

• Ionic compound becomes hydrated
• Surrounded by polar water molecules
• Attracted to the charged ions

Question 19

Why is water a good solvent for short chain alcohols?

Answer 19

• Can form hydrogen bonds with the water molecules

Question 20

Why are longer alcohol chains less soluble?

Answer 20

• Hydrocarbon chain is long
• Hydrogen bonds between water have to be broken
• Hydrogen bonds between alcohol have to be broken
• More bonds broken than formed
• Hydrogen end can only form weak electrostatic forces of attraction

Question 21

Why is water a poor solvent for non-polar molecules?

Answer 21

• Halogenoalkanes not polar enough to dissolve in water
• Cannot form hydrogen bonds
• Form weak intermolecular forces of attraction

Question 22

Why are non-aqueous solvents better for halogenoalkanes?

Answer 22

• Strength of intermolecular forces between solvent and solute similar