Chapter 21-24

Which energy charge with sign always positive?

• Bond energy

• enthalpy change of formation

• lattice energy

• electron affinity

What is meant by the term enthalpy change of atomisation?

• enthalpy change when one mole atoms is formed.

• enthalpy change when one mole gaseous atoms is formed.

• enthalpy change when one mole molecules is broken into its atoms.

• enthalpy change when one mole molecules is broken into its gaseous atoms.

The overall reaction for the atomisation of liquid bromine molecules, Br₂(l), is shown.

Calculate the enthalpy change of vaporisation of Br₂(l), ∆H^o_vap.

Bond energy(Br-Br) = 193 kJ mol^-1

The enthalpy change of atomisation of bromine, ∆H_at, = +112 kJ mol^–1.  

• -81 kJ mol^-1

• +305 kJ mol^-1

• +31 kJ mol^-1

• +417 kJ mol^-1

How the ∆H^o_vap of iodine, I₂(l), would compare to that of bromine, Br₂(l).

• more endothermic

• less endothermic

• same

How the enthalpy change of hydration of Br^–(g) would compare to that of I^–(g). 

• more exothermic

• less exothermic

• same

H₂SO₄ is considered a strong acid whereas HSO₄^– is considered a weak acid.

Suggest how the magnitude of the acid dissociation constant K_a1 for stage 1 compares to stage 2, K_a2. 

• K_a1 is larger than K_a2.

• K_a1 is smaller than K_a2.

• K_a1 is same as K_a2.

• Uncomparable

Benzoic acid, C₆H₅CO₂H, is a weak acid. A solution of 0.0250 mol dm^–3 benzoic acid has a pH of 2.90. Calculate the K_a of benzoic acid.

Write answer in decimal place form with 3 sf and no unit (e.g 0.0000100).

Which can be the electrolyte? (Answer can be more than one)

• NaCl (s)

• NaCl (l)

• NaCl (aq)

• Na (l)

Predict the products of the electrolysis of concentrated aqueous sodium chloride using graphite electrodes.

• Anode: oxygen
  Cathode: hydrogen

• Anode: oxygen

  Cathode: sodium

• Anode: chlorine

  Cathode: hydrogen

• Anode: chlorine

  Cathode: sodium

Predict the products of the electrolysis of aqueous silver nitrate using graphite electrodes.

• Anode: Oxygen
  Cathode: Hydrogen

• Anode: Hydrogen
  Cathode: Oxygen

• Anode: Oxygen
  Cathode: Silver

• Anode: Hydrogen
  Cathode: Oxygen