2009 Atoms, Bonds and Groups Jun

Question 1

Describe what you see when magnesium reacts with an excess of sulfuric acid

Answer 1

• Mg/solid dissolves

* Bubbles/ gas produced

Question 2

Compare and explain the electrical conductivities of sodium and sodium oxide in the solid and liquid states

Answer 2

• Sodium is a (good) conductor because it has mobile
electrons OR delocalised electrons
• Sodium oxide does not conduct as a solid
• Sodium oxide conducts when it is a liquid
• Ions cannot move in a solid
• Ions can move OR are mobile when liquid

Question 3

Explain why the first ionisation energies show a general increase from Li to Ne

Answer 3

• Atomic radii decreases
• Nuclear charge increases
• Shielding remains the same

Question 4

Explain the difference in first ionisation energies of Li and Na

Answer 4

• Atomic radii increase
• There is more shielding
• The nuclear attraction decreases

Question 5

Suggest why the second ionisation energy of oxygen has a greater value than the first ionisation energy

Answer 5

• The O+ ion, is smaller than the O atom
• Shielding is smaller
• The proton : electron ratio in the 2+ ion is greater than in the 1+ ion

Question 6

Explain with a diagram why the intermolecular forces in H2O that lead lead to the relatively high boiling point of H2O

Answer 6

• H-bond between H in one water molecule and a lone pair of an O in another water molecule

Question 7

Suggest why H2S has a much lower boiling point than H2O

Answer 7

• No hydrogen bonding

* Weaker intermolecular forces

Question 8

Explain why halogens show this trend in halogens

Chlorine -35
Bromine 59
Iodine 184

Answer 8

• Induced dipole interactions
• Number of electrons increases
• Down the group, more energy needed to break
intermolecular forces

Question 9

Stage 1
The student bubbled some chlorine through an aqueous solution of potassium iodide.

What would the student see at stage 1?

Answer 9

• Goes yellow/ brown /orange

Question 10

Stage 1
The student bubbled some chlorine through an aqueous solution of potassium iodide.

Name the products and write an ionic equation for the reaction in stage 1.

Answer 10

• Iodine and (potassium) chloride

* Cl2 + 2I– -> I2 + 2Cl–

Question 11

Stage 1
The student bubbled some chlorine through an aqueous solution of potassium iodide.

Why does the reaction in stage 1 occur?

Answer 11

• Chlorine / Cl2 is more reactive (than iodine)

* Chlorine / Cl2 is a more powerful oxidising agent

Question 12

Stage 1
The student bubbled some chlorine through an aqueous solution of potassium iodide.

Stage 2 The student added an organic solvent and shook the mixture.

What would the student see at stage 2?

Answer 12

• Goes purple / violet / lilac / pink