H2 Chemistry Flashcards

What is the mechanism for the reaction of benzene with bromine in the presence of AlBr₃?

Answer: Electrophilic substitution

AlBr₃ acts as a Lewis acid catalyst, generating Br⁺ (electrophile). Benzene undergoes electrophilic substitution to maintain aromaticity, replacing H with Br.

What is the pH of a buffer solution containing 0.1 mol/dm³ ethanoic acid (Ka = 1.8×10⁻⁵) and 0.1 mol/dm³ sodium ethanoate?

Answer: 4.74

Using Henderson-Hasselbalch: pH = pKa + log([A⁻]/[HA]) = -log(1.8×10⁻⁵) + log(1) = 4.74 + 0 = 4.74.

Which species is the oxidising agent in: MnO₄⁻ + 8H⁺ + 5Fe²⁺ → Mn²⁺ + 4H₂O + 5Fe³⁺?

Answer: MnO₄⁻

MnO₄⁻ is reduced (Mn goes from +7 to +2), so it is the oxidising agent. Fe²⁺ is oxidised to Fe³⁺ (loses electrons), making it the reducing agent.

What is the shape of SF₆?

Answer: Octahedral

SF₆ has 6 bonding pairs and no lone pairs around sulfur. VSEPR theory predicts an octahedral shape with 90° bond angles.

What is Le Chatelier's principle?

Answer: When a change is imposed on a system at equilibrium, the system shifts to oppose that change

Le Chatelier's principle states that if a system at equilibrium is disturbed, it will shift in a direction that tends to oppose the change, restoring a new equilibrium.

What functional group is present in an amide?

Answer: –CO–NH–

Amides contain the functional group –CONH– (or –CO–NH–), consisting of a carbonyl group (C=O) directly bonded to a nitrogen atom.