📚 Year 13 CCEA Chemistry Unit Test Mock Paper Walkthrough | Year 13 CCEA 化学单元测试模拟卷解析
This walkthrough breaks down a mock unit test designed for Year 13 CCEA Chemistry students, covering core AS topics from atomic structure to organic analysis. Each question is explained step by step, highlighting exam technique and common pitfalls.
本文为Year 13 CCEA化学学生解析一份模拟单元测试卷，涵盖原子结构到有机分析等核心AS主题。每道题目均逐步讲解，强调应试技巧和常见错误。
1. Multiple-Choice: Electron Configuration of Fe²⁺ | 选择题：Fe²⁺的电子排布
This question tests your ability to apply the rules for writing electron configurations of transition metal ions. Many students mistakenly remove 3d electrons first because they believe the highest energy level loses electrons first.
本题考察应用过渡金属离子电子排布规则的能力。许多同学错误地先移除3d电子，因为他们认为最高能级先失去电子。
nfiguration is [Ar] 3d⁶ 4s². When forming Fe²⁺, the two electrons are removed from the 4s subshell, not 3d, because in cations the 4s electrons experience a higher effective nuclear charge and are lost first.
对于铁(Z=26)，基态排布是 [Ar] 3d⁶ 4s²。形成Fe²⁺时，两个电子从4s亚层失去，而非3d，因为在阳离子中4s电子受到更高的有效核电荷，优先失去。
Therefore, the correct configuration is [Ar] 3d⁶, which corresponds to option B. Watch out for options that keep the 4s electrons or remove from 3d.
因此，正确答案是 [Ar] 3d⁶，对应选项B。要警惕那些保留4s电子或从3d移除电子的迷惑项。
2. Stoichiometry: Gas Volume from a Reaction | 化学计量：反应生成气体体积
A classic calculation: 25.0 cm³ of 0.100 mol dm⁻³ Na₂CO₃ reacts with excess HCl. Use the balanced equation to find moles and then apply molar volume at RTP.
经典计算题：25.0 cm³ 0.100 mol dm⁻³ 的Na₂CO₃与过量HCl反应。利用配平的方程式求物质的量，再应用RTP下的摩尔体积。
Na₂CO₃ + 2HCl → 2NaCl + H₂O + CO₂
0.00250 mol. From the equation, 1 mol Na₂CO₃ produces 1 mol CO₂, so n(CO₂) = 0.00250 mol.
首先，Na₂CO₃的物质的量：n = cV = 0.100 mol dm⁻³ × 0.0250 dm³ = 0.00250 mol。根据方程式，1 mol Na₂CO₃ 生成 1 mol CO₂，因此 n(CO₂) = 0.00250 mol。
s to 60.0 cm³. A frequent mistake is forgetting to convert cm³ to dm³ for concentration-volume calculations.
CO₂体积 = n × 24.0 dm³ mol⁻¹ = 0.00250 × 24.0 = 0.0600 dm³，换算为 60.0 cm³。常见错误是在浓度-体积计算中忘记将cm³转换为dm³。
3. Enthalpy Cycles: Hess's Law for ΔHf° | 焓循环：利用盖斯定律求标准生成焓
Given combustion data, construct a Hess cycle to find the standard enthalpy of formation of ethanol. This requires careful handling of signs.
已知燃烧数据，构建盖斯循环求乙醇的标准生成焓。这需要仔细处理正负号。
ΔHc°(C(s)) = -394 kJ mol⁻¹, ΔHc°(H₂(g)) = -286 kJ mol⁻¹, ΔHc°(C₂H₅OH(l)) = -1367 kJ mol⁻¹.
Published by TutorHao | Year 13 Chemistry Revision Series | aleveler.com
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