Neco 2025 Chemistry Question 3

Practice essay / theory question 3 from the 2025 Neco Chemistry examination. This question covers Chemical Bonding .

Neco 2025 Chemistry Essay / Theory

Topic: Chemical Bonding

Question 3 NECO • 2025 • CHEMISTRY • essay

Element X has an electronegativity of 1.5 and element Y has an electronegativity of 3.0. They combine to form a binary compound XY. The compound is a solid at room temperature, conducts electricity when molten, and is highly soluble in water.

Question Parts

( a )

Calculate the electronegativity difference (ΔEN) between X and Y and use Pauling's empirical formula \(\text{Percent ionic character}=\left(1-e^{-0.25(\Delta EN)^2}\right)\times100\) to determine the percent ionic character of the XY bond. Show all steps.

( b )

Based on the percent ionic character obtained, classify the XY bond as ionic, polar covalent or non‑polar covalent. Justify your classification with reference to typical percentage ranges.

( c )

Predict three physical properties of XY – (i) melting point, (ii) electrical conductivity in the molten state, and (iii) solubility in water – and explain how the polar covalent nature of the bond influences each property.

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About This Question

This is Neco 2025 Chemistry Question 3. It is one of the essay questions from the 2025 Neco Chemistry examination.

The question covers Chemical Bonding .

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