Neco 2018 Chemistry Question 3

Practice essay / theory question 3 from the 2018 Neco Chemistry examination. This question covers Chemical Bonding .

Neco 2018 Chemistry Essay / Theory

Topic: Chemical Bonding

Question 3 NECO • 2018 • CHEMISTRY • essay

A compound X is formed between a metal M and a non‑metal N. The metal M has an atomic radius of 160 pm, a first ionisation energy of 735 kJ mol⁻¹ and a sublimation enthalpy of 100 kJ mol⁻¹. The non‑metal N has an electronegativity of 3.0, a first electron affinity of –150 kJ mol⁻¹, a second electron affinity of –200 kJ mol⁻¹ and a bond dissociation energy for N₂ of 495 kJ mol⁻¹. The lattice energy of the ionic solid X is –3500 kJ mol⁻¹. The compound is known to be ionic.

Question Parts

( a )

Write the electron configurations of the neutral atoms M and N, and of the ions M⁺ and N⁻ that are present in X.

( b )

Using the data given, calculate the standard enthalpy change (ΔH⁰_f) for the formation of one mole of X from its elements in their standard states, employing a Born‑Haber cycle.

( c )

Explain, with reference to the data, why the formation of X is thermodynamically favourable despite the relatively high first ionisation energy of M.

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About This Question

This is Neco 2018 Chemistry Question 3. It is one of the essay questions from the 2018 Neco Chemistry examination.

The question covers Chemical Bonding .

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