CAPE Chemistry June 2018 Ul P2 Ql - Answer
l(a)
The overall energy change for a chemical reaction is the same whatever
route is taken.
l(b)(i)
8H 1: Enthalpy of atomization of potassium.
8H 2: Enthalpy of atomization of fluorine.
8H3: 1st ionization energy of potassium.
8H4: 1st electron affinity of fluorine.
l(b)(ii)
Lattice energy
=-562.6- (89.6 +419.0 + 79.1-332.6).
=-562.6-255.1.
= 817.7 kJ mo1·1.
l(b)(iii)
Closeness of agreement between the theoretical and experimental lattice
energy values suggest that there is ionic bonding in an ionic lattice. This
results from the high difference in electronegativity between the ions
present.
l(c)
Transfer 50 cm3 of KOH into a Styrofoam cup, using a pipette.
Record the temperature of the KOH solution.
Record the temperature of the HCI.
Place acid in a burette.
Add acid to alkali in 5 cm3 portions, mixing and recording the highest
temperature.
UsingT 1 = KOH temperature,T2 = HCI temperature,T3 = highest temperature,
8H = 100 g x 4.18 x 8T k J