Chemistry Flashcards

What type of bonding exists in a sodium chloride (NaCl) crystal as studied in Singapore A-Level Chemistry?

Answer: Ionic bonding — electrostatic attraction between Na⁺ and Cl⁻ ions

NaCl consists of Na⁺ and Cl⁻ ions held together by strong electrostatic forces of attraction in a giant ionic lattice structure. Sodium transfers its valence electron to chlorine.

According to Le Chatelier's Principle, what happens when pressure is increased on the equilibrium N₂ + 3H₂ ⇌ 2NH₃?

Answer: Equilibrium shifts to the right (towards fewer moles of gas)

Increasing pressure favours the side with fewer moles of gas. Left side has 4 moles (1 + 3); right side has 2 moles. Equilibrium shifts right to produce more ammonia.

What is the hybridisation of carbon in methane (CH₄)?

Answer: sp³

In methane, carbon forms four equivalent C-H bonds by hybridising its 2s and three 2p orbitals to form four sp³ hybrid orbitals, resulting in a tetrahedral shape with 109.5° bond angles.

What is the oxidation state of manganese in KMnO₄?

Answer: +7

In KMnO₄: K is +1, each O is -2 (total -8). So +1 + Mn + (-8) = 0, giving Mn = +7. Manganese is in its highest common oxidation state.

What is the rate-determining step in a reaction mechanism?

Answer: The slowest step that determines the overall rate of reaction

The rate-determining step is the slowest step in a multi-step reaction mechanism. It acts as a bottleneck, controlling the overall rate of the reaction.

In the Singapore A-Level syllabus, what is an SN2 reaction?

Answer: A bimolecular nucleophilic substitution with a single concerted step, resulting in inversion of configuration

SN2 (Substitution Nucleophilic Bimolecular) involves a single concerted step where the nucleophile attacks the carbon from the opposite side to the leaving group, causing Walden inversion of stereochemistry.