AQA As Chemistry Paper 1 2025 Mark Scheme Pdf

Download the official AQA AS Chemistry Paper 1 mark scheme for the June 2025 exam (7404/1). This is the **final version (v1.0)** used by examiners during standardisation, containing full answers, mark allocations, and detailed guidance on how marks are awarded.

The mark scheme provides complete solutions for all **Inorganic and Physical Chemistry** questions:

**Section A (structured questions):**
- **Question 1 (pages 11–12):** Atom economy calculated as **77.2%**, plus full equation for titanium extraction (*TiCl₄ + 2Mg → 2MgCl₂ + Ti*) and explanation of magnesium as a reducing agent.
- **Question 2 (pages 13–15):** Halogen chemistry including:
- Trend explanation (stronger London forces down the group)
- Chlorine use in water (kills bacteria safely at low concentration)
- Disproportionation equations such as *2NaOH + Cl₂ → NaCl + NaClO + H₂O*
- Oxidation state of chlorine in NaClO₃ = **+5**
- **Question 3 (pages 16–19):** Atomic structure and mass spectrometry:
- Electron configuration of F⁻
- Identification of Mn from electron configuration
- Relative atomic mass calculation = **52.1** (from Table 2 on page 9 of the paper)
- Ion mass calculation using KE formula giving **8.63 × 10⁻²³ g**
- **Question 4 (pages 20–21):** Group 2 trends including weaker metallic bonding down the group and reaction of barium with water:
- *Ba + 2H₂O → Ba(OH)₂ + H₂*
- **Question 5 (page 22):** Titration calculation:
- Mean titre = **10.60 cm³**
- Final Mr of H₂A = **≈104**
- Percentage uncertainty ≈ **1.41%**
- **Question 6 (pages 23–24):** Qualitative analysis using Table 4:
- Solution A identified as **BaCl₂ / SrCl₂**
- Solution B identified as **(NH₄)₂CO₃ / NH₄HCO₃**
- Includes ionic equations such as *Ba²⁺ + SO₄²⁻ → BaSO₄*
- **Question 7 (pages 25–27):** Equilibrium:
- Graph interpretation (HI increases from zero to equilibrium)
- Temperature increase shifts equilibrium right (endothermic reaction)
- Kc calculation = **~1.7 mol⁻² dm⁶**

**Section B (multiple-choice answers, pages 28–29):**
All correct answers are provided, for example:
- Q9: **2261 kg** (ideal gas calculation)
- Q14: **Si** (ionisation energy trend)
- Q18: **D** (greatest temperature rise)
- Q19: **SCl₂** (polar molecule)
- Q21: **1225 cm³** (dilution calculation)

The mark scheme also includes detailed examiner guidance such as:
- Error carried forward (ECF) rules
- Marking of calculations and working
- Rules for equations, significant figures, and units
- Level-of-response marking for 6-mark questions (Question 6.1)

For example, the **levels of response table on page 23** explains how students must link observations to conclusions and include correct ionic equations to achieve full marks.

This resource is essential for understanding exactly how marks are awarded, improving exam technique, and mastering calculations and explanations required for top grades in AS Chemistry.

Fully updated for the 2025/2026 academic year and optimised for instant download on markscheme.net.

This mark scheme is ideal for Year 12 students preparing for AQA AS Chemistry exams or Year 13 students revising core fundamentals for A-Level Chemistry.

Teachers and tutors use this resource to standardise marking, provide accurate feedback, and demonstrate full-mark answers. It is also perfect for independent learners who want to understand examiner expectations in detail.