Waec Model Questions Vol1 2019 Chemistry Question 1

Practice essay / theory question 1 from the 2019 Waec Model Questions Vol1 Chemistry examination. This question covers Atomic Structure .

Waec Model Questions Vol1 2019 Chemistry Essay / Theory
Topic: Atomic Structure
Question 1 WAEC_MODEL_QUESTIONS_VOL1 • 2019 • CHEMISTRY • essay
Waec Model Questions Vol1 2019 Chemistry Question 1 diagram

The diagram shows a simplified Bohr model of an unknown element X. The nucleus contains 15 protons and 16 neutrons. The electron shells are drawn with 2 electrons in the first shell, 8 electrons in the second shell and 5 electrons in the outermost shell.

Question Parts

( a )
Identify the element and write its chemical symbol together with its atomic number.
( b )
Write the ground‑state electron configuration of the element using the long‑form notation (e.g., 1s² 2s² 2p⁶ …).
( c )
The element forms a binary ionic compound with oxygen having the formula X₂O₃. (i) Determine the oxidation state of X in this compound. (ii) Calculate the mass percent of X in X₂O₃. (Use atomic masses: P = 30.97 g mol⁻¹, O = 16.00 g mol⁻¹.)
( d )
If 0.250 mol of X₂O₃ is thermally decomposed according to the equation X₂O₃ → 2 X + 3⁄2 O₂, calculate the volume of O₂ gas released at STP (22.4 L mol⁻¹).

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About This Question

This is Waec Model Questions Vol1 2019 Chemistry Question 1. It is one of the essay questions from the 2019 Waec Model Questions Vol1 Chemistry examination.

The question covers Atomic Structure .

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