2011 Atoms, Bonds and Groups Jun

Question 1

Define the first ionisation energy

Answer 1

• The energy required to remove an electron
• From each atom in one mole
• Of atoms in the gaseous state

Question 2

Explain what is meant by the term periodicity

Answer 2

• A repeating pattern across period

Question 3

Give the systematic name for NaClO

Answer 3

• Sodium chlorate(V)

Question 4

Reason for/against adding chlorine to water

Answer 4

Against
• Chlorinated hydrocarbons are carcinogens
• Chlorine is toxic/poisonous

For
• (Chlorine) kills bacteria
• ‘Sterilises water’ OR ‘disinfects

Question 5

Describe a simple chemical test that you could carry out to show that aqueous NaCl contains aquesous chloride ions. How would you confirm that no other halide ions are present?

Answer 5

• Add AgNO3(aq) OR Ag+(aq) OR silver nitrate OR
AgNO3
• White precipitate 
• Ag+ + Cl– -> AgCl
• Add dilute NH3 and precipitate (completely) dissolves
OR disappear

Question 6

Explain why ZCl2 is a salt

Answer 6

• H+ are replaced by zinc ions OR Zn2+

Question 7

Describe and explain the trend in reactivity of the Group 2 elements with dilute HCl acid as the group descended

Answer 7

• Reactivity increases (down the group) 
• atomic radii increases 
• there is more shielding
• The nuclear attraction decreases 
• Easier to remove (outer) electrons
OR ionisation energy decreases

Question 8

Giant metallic lattices conduct electricty. Giant ionic lattices do not, however if melted giant ionic lattices conduct electricity

Explain why

Answer 8

• Metallic lattice has delocalised electrons
• Ionic lattice has no mobile ions
• Molten ionic (compounds) have mobile ions

Question 9

Suggest why ice has a higher melting point than solid ammonia

Answer 9

• Ice has stronger hydrogen bonds
• O has two lone pairs (AND N has one)
• O more electronegative (than N)

Question 10

What is the lattice structure in solid SiO2 and in solid SiCl4 explain the difference in melting points in terms of bonding and structure

Answer 10

• SiO2 is giant covalent (lattice)
• SiCl4 is simple molecular (lattice)
• van der Waals’ forces in SiCl4
• Covalent bonds broken in SiO2
• Forces OR bonds are stronger in SiO2 (than in SiCl4)