Year 12 Edexcel Chemistry: Unit Test Mock Paper Walkthrough | Year 12 Edexcel 化学：单元测试模拟卷解析

📚 Year 12 Edexcel Chemistry: Unit Test Mock Paper Walkthrough | Year 12 Edexcel 化学：单元测试模拟卷解析

This article provides a detailed walkthrough of a mock unit test for Year 12 Edexcel Chemistry. By working through carefully selected exam-style questions and their solutions, you will reinforce key concepts from atomic structure, amount of substance, bonding, energetics, organic chemistry, kinetics, and equilibrium. The format mirrors the Edexcel AS assessment style, helping you build confidence and exam technique.

本文详细解析了一套针对 Year 12 Edexcel 化学的单元模拟测试卷。通过逐题讲解精选的考试风格问题和解答，你将巩固原子结构、物质量、化学键与结构、能量学、有机化学、动力学和平衡等核心知识点。格式与 Edexcel AS 评估风格一致，有助于提升你的信心和应试技巧。

1. Atomic Structure and First Ionisation Energy Trends | 原子结构与第一电离能趋势

Question: The first ionisation energies (in kJ mol⁻¹) of five consecutive elements from Period 3 are listed.

问题：列出了第三周期五种连续元素的第一电离能（单位 kJ mol⁻¹）。

Na: 496, Mg: 738, Al: 578, Si: 789, P: 1012

Na: 496, Mg: 738, Al: 578, Si: 789, P: 1012

Explain the general increase across the period and the fall from Mg to Al. Use the electronic configurations to support your answer.

解释电离能总体递增趋势以及 Mg 到 Al 的下降，并利用电子构型支持你的答案。

Solution: The general increase is due to greater nuclear charge, while shielding remains similar as electrons are added to the same outer shell. The attraction between nucleus and outermost electron strengthens, so more energy is required to remove it.

解析：总体递增是因为核电荷增大，而屏蔽效应几乎不变（电子增加在同一主层），原子核对外层电子的吸引力增强，移除电子需要更多能量。

The drop from Mg (1s²2s²2p⁶3s²) to Al (1s²2s²2p⁶3s²3p¹) occurs because the outermost electron in Al is in a 3p orbital, which is of higher energy and further from the nucleus than the 3s orbital in Mg. Thus, less energy is needed to remove it. Additionally, the 3p electron is shielded by the 3s² electrons, further reducing effective nuclear attraction.

从 Mg（1s²2s²2p⁶3s²）到 Al（1s²2s²2p⁶3s²3p¹）的下降是因为铝的最外层电子位于 3p 轨道，3p 轨道的能量高于镁的 3s 轨道，且离核更远，因此移出电子所需能量较少。此外，3p 电子被 3s² 电子屏蔽，有效核引力进一步降低。

2. Empirical Formula and Water of Crystallisation | 经验式与结晶水

Question: A hydrated magnesium sulfate salt, MgSO₄·xH₂O, has a mass of 4.92 g. After heating to constant mass, the anhydrous MgSO₄ weighs 2.40 g. Determine the value of x.

问题：某水合硫酸镁 MgSO₄·xH₂O 质量为 4.92 g。加热至恒重后，无水 MgSO₄ 质量为 2.40 g。求 x 的值。

Published by TutorHao | Year 12 Chemistry Revision Series | aleveler.com

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