2017

Question 1

Define the term enthalpy of lattice formation (2 marks)

Answer 1

Enthalpy change is when 1 mol of solid ionic compound or 1 mol of ionic lattice is formed from its gaseous ions

Question 2

how to calculate enthalpy of lattice formation (2)

Answer 2

sum of all changes = lattice enthalpy

changes cud be -
- ionisation of atoms
- bond disassociation
- atomisation
- electron affinity
- formation of 1 mole of solid crystal from gaseous ions

Question 3

why does the calculation of the enthalpy of silver iodide based on a perfect ionic model give a smaller numerical value that to it being calculated otherwise (2)

Answer 3

Because silver iodide contains covalent character and its bonds (holding the lattice together) are stronger

Question 4

what is Agl

Answer 4

silver iodide

Question 5

what is a reagent that cud be used to indicate the prescence of iodide ions in an aqueous solution and what would be the observations made? (2)

Answer 5

AgNO₃ and it would become yellow ppt
OR
Cl₂ or Br₂ and it would become a brown solution or black ppt
(parts per trillion?)

Question 6

Maths questions in this paper?

Answer 6

01.2
02.1
02.2
03.2
03.4
04.1

Question 7

what is the correct expression for Kᵚ

Answer 7

Kᵚ = [H+][OH-]

(+- = small)

Question 8

suggest why pure water at 10 degrees is not alkaline?

Answer 8

[H+] = [OH-]

Question 9

pH of magnesium hydroxide compared to calcium hydroxide at 10 degrees

Answer 9

mgh will have a lower pH because it is less soluble