CCEA A2 Chemistry is won on titration precision, transition metal chemistry and organic nitrogen work. This page shows exactly where the marks sit across all four units, the timing per paper, and the exam habits examiners repeatedly reward or penalise.
อ่าน 3 นาทีอัปเดตเมื่อ: 3 ก.ย. 2569
ภาพรวมข้อสอบ
จำนวนฉบับ
4
คะแนนเต็ม
310
เวลาสอบ
6ชม. 30นาที
ประเภทคำถาม
12
ฉบับ
เวลา
คะแนน
จำนวนข้อ
น้ำหนักคะแนน
ประเภทคำถาม
A2 1: Further physical & organic chemistry
2ชม.
110
17
35.5%
Multiple choice, Structured calculations and short answer, Extended response (banded QWC)
Qualitative test observations and temperature recording
A2 3: Practical theory
1ชม. 15นาที
60
4
19.3%
Apparatus drawing and experimental description, Organic synthesis and purification procedure, Quantitative analysis and back titration calculations
เกณฑ์เกรด
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ข้อกำหนดเครื่องคิดเลข
A scientific calculator is expected for every paper in this subject. CCEA follows the JCQ rule that applies across all its exams: no calculator with a computer algebra system or symbolic manipulation function, no borrowing a calculator from another candidate, and nothing stored in memory that could be retrieved during the exam, including formulae, notes or text. If your calculator has an exam mode, switch it on. It clears stored data far more reliably than the reset button, which only resets display settings and leaves any stored programs or text in memory.
AO1: AO1: demonstrate knowledge and understanding of scientific ideas, processes, techniques and procedures (33%)
AO2: AO2: apply that knowledge and understanding in theoretical and practical contexts and when handling qualitative and quantitative data (42%)
AO3: AO3: analyse, interpret and evaluate scientific information, ideas and evidence to make judgements and reach conclusions, and to develop and refine practical design and procedures (25%)
วัตถุประสงค์: Keeps a multi-step redox titration calculation, such as a dichromate-thiosulfate sequence, accurate by carrying an exact value through several stages instead of retyping a rounded one.
ใช้เมื่อใด: Any redox or back-titration question with more than one calculation stage and an awkward mole ratio such as 1 to 6.
ขั้นตอน
Calculate moles at the first stage as normal, then press the memory-store key (M+ or STO) instead of writing down a rounded figure. At the next stage, press memory-recall (MR or RCL) to bring the exact value back and continue from there.
ข้อควรระวังในการสอบ: This works only with values calculated live in the exam. Nothing may be stored in a calculator's memory before the exam, including formulae or old working, so clear memory and switch on exam mode if your calculator has one before you sit down.
Keep stoichiometric ratios exact with fraction mode
Casio fx-83/85 series (scientific)
วัตถุประสงค์: Keeps the arithmetic exact through several steps and makes it easier to spot when the wrong ratio has been applied.
ใช้เมื่อใด: Any redox or acid-base equation with an awkward stoichiometric ratio that would otherwise need early rounding.
ขั้นตอน
Enter the ratio using the a-b/c fraction key rather than converting to a decimal straight away, and carry that fraction through the rest of the calculation before converting to a decimal at the final answer line.
ข้อควรระวังในการสอบ: Use this as an in-exam working method only. A calculator with a computer algebra system or any stored formula list is not permitted under CCEA's rules.
Convert units live before substituting into thermodynamic equations
Casio fx-83/85 series (scientific)
วัตถุประสงค์: Stops a joule to kilojoule or Celsius to kelvin slip from breaking a \(\Delta G = \Delta H - T\Delta S\) calculation.
ใช้เมื่อใด: Any free energy, entropy or enthalpy question where the given units do not already match.
ขั้นตอน
Before substituting into \(\Delta G = \Delta H - T\Delta S\), do the unit conversion, J to kJ or degrees Celsius to kelvin, as its own calculator step and write the converted value on your answer line before continuing.
ข้อควรระวังในการสอบ: This is a technique for the exam itself, not something to prepare in advance. Your calculator must be cleared of any stored data or formulae before the exam starts.
ข้อผิดพลาดที่พบบ่อย
1mediumคะแนนที่เกี่ยวข้อง: 1Volumetric analysis
Describing a solution as 'clear' when they mean 'colourless', or the other way round.
วิธีหลีกเลี่ยง: Use colourless for the absence of colour and keep clear for the absence of cloudiness. A solution can be clear and blue at the same time.
2highคะแนนที่เกี่ยวข้อง: 2Volumetric analysis
Including a non-concordant rough titre when calculating the mean accurate titre.
วิธีหลีกเลี่ยง: Only average titres that agree within 0.10 cm3 of each other, and state clearly which values were excluded before giving the mean.
3highคะแนนที่เกี่ยวข้อง: 3Enthalpy, entropy and free energy
Mixing joules and kilojoules when substituting into \(\Delta G = \Delta H - T\Delta S\), particularly forgetting entropy is usually given in J per K per mole while enthalpy is in kJ per mole.
วิธีหลีกเลี่ยง: Convert entropy to kJ per K per mole by dividing by 1000 before substituting, and write that conversion as its own line of working.
4mediumคะแนนที่เกี่ยวข้อง: 2Carboxylic acids
Omitting a factor of two in dibasic acid or diprotic reactions when calculating reacting quantities in esterification and back titrations.
วิธีหลีกเลี่ยง: Write the balanced equation first and read the mole ratio directly off it before calculating, rather than assuming a one to one ratio.
5mediumคะแนนที่เกี่ยวข้อง: 2Transition metals
Missing charges or writing the wrong coordination number for complex ions during ligand substitution reactions.
วิธีหลีกเลี่ยง: Write the full formula of the complex ion in square brackets with its overall charge before balancing the substitution equation.
6mediumคะแนนที่เกี่ยวข้อง: 2Nuclear magnetic resonance spectroscopy
Confusing peak integration values with splitting pattern multiplicities in proton NMR spectra.
วิธีหลีกเลี่ยง: Keep the two separate: integration tells you how many protons sit in an environment, splitting under the n plus 1 rule tells you how many non-equivalent protons are next door.
7mediumคะแนนที่เกี่ยวข้อง: 3Lattice enthalpy
In Born-Haber cycles, omitting fractional coefficients such as one half for diatomic gaseous halogens or hydrogen, or leaving out state symbols.
วิธีหลีกเลี่ยง: Balance the equation for one mole of the compound and write full state symbols on every step of the cycle before drawing the arrows.
8highคะแนนที่เกี่ยวข้อง: 2Volumetric analysis
In QWC practical descriptions, omitting procedural steps such as rinsing glassware with the solution it will hold, or adding acid dropwise near the titration endpoint.
วิธีหลีกเลี่ยง: Build a short checklist of standard technique steps for volumetric work and tick through it mentally before writing the answer, not just the chemistry.