Chemistry Flashcards

Which of the following compounds shows geometrical isomerism?

Answer: 2-butene

2-Butene (CH₃–CH=CH–CH₃) shows cis-trans geometrical isomerism because each double-bond carbon has two different substituents.

In the Born-Haber cycle for NaCl formation, which step is endothermic?

Answer: Sublimation of Na

Sublimation of solid sodium to gaseous atoms is endothermic as energy must be supplied to overcome metallic bonding.

The half-life of a first-order reaction is 693 seconds. The rate constant is approximately:

Answer: 0.001 s⁻¹

For a first-order reaction, k = 0.693/t½ = 0.693/693 = 0.001 s⁻¹.

Which of the following is NOT a transition element?

Answer: Zinc (Zn)

Zinc (Zn, [Ar]3d¹⁰4s²) is not a transition element because its d-orbitals are completely filled in both the element and its common ion (Zn²⁺).

Which of the following is the correct order of boiling points of noble gases?

Answer: He < Ne < Ar < Kr < Xe

Boiling points of noble gases increase with atomic mass due to increasing London dispersion forces: He < Ne < Ar < Kr < Xe.

The product formed when aniline reacts with NaNO₂ and HCl at 0–5°C is:

Answer: Benzene diazonium chloride

Aniline undergoes diazotization with NaNO₂/HCl at 0–5°C to form benzene diazonium chloride (C₆H₅N₂⁺Cl⁻).

Which of the following colligative properties is used to determine the molecular weight of macromolecules?

Answer: Osmotic pressure

Osmotic pressure is preferred for macromolecules because even dilute solutions give measurable osmotic pressure, unlike the small changes in other colligative properties.