{
"schema_version": "1.1.0",
"archetypes": [
{
"id": "KP_FROM_EQUILIBRIUM_MOLES",
"version": "1.0.0",
"module": "EQUILIBRIUM_CALCULATIONS",
"epic": "KC_KP",
"scope": "Calculate Kp from equilibrium moles and total pressure for one ideal-gas equilibrium.",
"allowed_variations": [
{
"id": "REORDERED_STUDENT_STEPS",
"description": "Student steps may be entered in a non-canonical sequence and aligned by kind.",
"constraints": [
"The frozen species, stoichiometry, givens and marking policy do not change."
]
}
],
"node_kinds": [
"BALANCED_EQUATION",
"EQUILIBRIUM_MOLES",
"TOTAL_MOLES",
"MOLE_FRACTIONS",
"PARTIAL_PRESSURES",
"KP_EXPRESSION",
"SUBSTITUTION",
"NUMERICAL_RESULT",
"UNIT",
"SIGNIFICANT_FIGURES"
]
}
],
"problems": [
{
"id": "CAIE9701-KP-EQM-001",
"version": "1.0.0",
"archetype_id": "KP_FROM_EQUILIBRIUM_MOLES",
"archetype_version": "1.0.0",
"curriculum": {
"board": "CAIE",
"syllabus_code": "9701",
"cycle": "2025-2027",
"module": "Equilibrium Calculations"
},
"prompt": "At equilibrium, a gas mixture contains 0.40 mol PCl5, 0.30 mol PCl3 and 0.30 mol Cl2. The total pressure is 2.00 x 10^5 Pa. For PCl5(g) reversible PCl3(g) + Cl2(g), calculate Kp and give the answer to two significant figures.",
"given_quantities": [
{
"id": "G-PCL5",
"symbol": "n(PCl5)",
"value": 0.4,
"unit": "mol",
"significant_figures": 2,
"species": "PCl5(g)"
},
{
"id": "G-PCL3",
"symbol": "n(PCl3)",
"value": 0.3,
"unit": "mol",
"significant_figures": 2,
"species": "PCl3(g)"
},
{
"id": "G-CL2",
"symbol": "n(Cl2)",
"value": 0.3,
"unit": "mol",
"significant_figures": 2,
"species": "Cl2(g)"
},
{
"id": "G-PTOTAL",
"symbol": "p(total)",
"value": 200000,
"unit": "Pa",
"significant_figures": 3,
"species": null
}
],
"chemical_equation": {
"reversible": true,
"species": [
{
"formula": "PCl5",
"phase": "g",
"coefficient": 1,
"side": "reactant"
},
{
"formula": "PCl3",
"phase": "g",
"coefficient": 1,
"side": "product"
},
{
"formula": "Cl2",
"phase": "g",
"coefficient": 1,
"side": "product"
}
]
},
"answer_requirements": {
"unit": "Pa",
"significant_figures": 2
},
"source_evidence": {
"type": "INTERNAL_AUTHORED_DRAFT",
"references": [
"https://www.cambridgeinternational.org/programmes-and-qualifications/cambridge-international-as-and-a-level-chemistry-9701/"
],
"claim_scope": "Draft practice problem aligned to the named syllabus family; not copied from or claimed equivalent to a past-paper question or mark scheme."
},
"review_status": "AI_DRAFT"
}
],
"solution_graphs": [
{
"id": "CAIE9701-KP-EQM-001-SG",
"version": "1.0.0",
"problem_id": "CAIE9701-KP-EQM-001",
"problem_version": "1.0.0",
"archetype_id": "KP_FROM_EQUILIBRIUM_MOLES",
"archetype_version": "1.0.0",
"nodes": [
{
"id": "N01",
"kind": "BALANCED_EQUATION",
"validator": "validateChemicalEquation",
"expected": "PCl5(g) <=> PCl3(g) + Cl2(g)",
"accepted_alternatives": [
"PCl5(g) ⇌ PCl3(g) + Cl2(g)"
]
},
{
"id": "N02",
"kind": "EQUILIBRIUM_MOLES",
"validator": "evaluateExpression",
"expected": {
"PCl5": 0.4,
"PCl3": 0.3,
"Cl2": 0.3
},
"accepted_alternatives": []
},
{
"id": "N03",
"kind": "TOTAL_MOLES",
"validator": "evaluateExpression",
"expected": {
"value": 1,
"unit": "mol"
},
"accepted_alternatives": []
},
{
"id": "N04",
"kind": "MOLE_FRACTIONS",
"validator": "validateMoleFractions",
"expected": {
"PCl5": 0.4,
"PCl3": 0.3,
"Cl2": 0.3
},
"accepted_alternatives": []
},
{
"id": "N05",
"kind": "PARTIAL_PRESSURES",
"validator": "validatePartialPressures",
"expected": {
"PCl5": 80000,
"PCl3": 60000,
"Cl2": 60000,
"unit": "Pa"
},
"accepted_alternatives": []
},
{
"id": "N06",
"kind": "KP_EXPRESSION",
"validator": "checkExpressionEquivalence",
"expected": "p(PCl3) * p(Cl2) / p(PCl5)",
"accepted_alternatives": [
"p(Cl2) * p(PCl3) / p(PCl5)"
]
},
{
"id": "N07",
"kind": "SUBSTITUTION",
"validator": "evaluateExpression",
"expected": "60000 * 60000 / 80000",
"accepted_alternatives": [
"(6.00e4 * 6.00e4) / 8.00e4"
]
},
{
"id": "N08",
"kind": "NUMERICAL_RESULT",
"validator": "evaluateExpression",
"expected": {
"value": 45000
},
"accepted_alternatives": []
},
{
"id": "N09",
"kind": "UNIT",
"validator": "convertUnit",
"expected": "Pa",
"accepted_alternatives": []
},
{
"id": "N10",
"kind": "SIGNIFICANT_FIGURES",
"validator": "checkSignificantFigures",
"expected": {
"value": 45000,
"formatted": "4.5 x 10^4 Pa",
"significant_figures": 2
},
"accepted_alternatives": [
"4.5e4 Pa"
]
}
],
"edges": [
{
"from": "N01",
"to": "N06",
"role": "defines exponents"
},
{
"from": "N02",
"to": "N03",
"role": "values summed"
},
{
"from": "N02",
"to": "N04",
"role": "species numerators"
},
{
"from": "N03",
"to": "N04",
"role": "common denominator"
},
{
"from": "N04",
"to": "N05",
"role": "fractions scaled by total pressure"
},
{
"from": "N05",
"to": "N07",
"role": "partial-pressure values"
},
{
"from": "N06",
"to": "N07",
"role": "substitution structure"
},
{
"from": "N07",
"to": "N08",
"role": "numeric evaluation"
},
{
"from": "N06",
"to": "N09",
"role": "dimensional result"
},
{
"from": "N08",
"to": "N10",
"role": "rounding source"
},
{
"from": "N09",
"to": "N10",
"role": "formatted answer unit"
}
]
}
],
"marking_policies": [
{
"id": "CAIE9701-KP-EQM-001-MP",
"version": "1.0.0",
"problem_id": "CAIE9701-KP-EQM-001",
"problem_version": "1.0.0",
"solution_graph_id": "CAIE9701-KP-EQM-001-SG",
"solution_graph_version": "1.0.0",
"source_evidence": {
"type": "INTERNAL_AUTHORED_DRAFT",
"claim_scope": "Development-only policy for this exact authored problem; not a claim about a live CAIE mark scheme."
},
"review_status": "AI_DRAFT",
"mark_nodes": [
{
"id": "M01",
"solution_node_id": "N03",
"criterion": "Correct total equilibrium moles",
"dependencies": [
"N02"
],
"marks": 1
},
{
"id": "M02",
"solution_node_id": "N04",
"criterion": "Correct species mole fractions",
"dependencies": [
"N02",
"N03"
],
"marks": 1
},
{
"id": "M03",
"solution_node_id": "N05",
"criterion": "Correct partial pressures",
"dependencies": [
"N04"
],
"marks": 1
},
{
"id": "M04",
"solution_node_id": "N06",
"criterion": "Correct Kp expression",
"dependencies": [
"N01"
],
"marks": 1
},
{
"id": "M05",
"solution_node_id": "N07",
"criterion": "Consistent substitution and numerical evaluation",
"dependencies": [
"N05",
"N06"
],
"marks": 1
},
{
"id": "M06",
"solution_node_id": "N09",
"criterion": "Correct unit",
"dependencies": [
"N06"
],
"marks": 1
},
{
"id": "M07",
"solution_node_id": "N10",
"criterion": "Answer to two significant figures",
"dependencies": [
"N08",
"N09"
],
"marks": 1
}
],
"ecf_rules": [
{
"id": "ECF-N03-DOWNSTREAM",
"trigger_node_id": "N03",
"eligible_downstream_nodes": [
"N04",
"N05",
"N07",
"N08"
],
"eligible_mark_nodes": [
"M02",
"M03",
"M05"
],
"award": {
"mode": "PRESERVE_ELIGIBLE_MARK_NODES",
"maximum_marks": 3
},
"conditions": [
"Student total moles is positive and derived from the stated equilibrium-moles step.",
"Downstream mole fractions and partial pressures are internally consistent with that total.",
"The chemical equation and Kp expression are independently correct."
],
"exclusions": [
"No ECF for a wrong species set, unbalanced equation, inverted Kp expression, unsupported unit, or independent arithmetic error."
]
}
]
}
],
"follow_up_problems": [
{
"problem_id": "CAIE9701-KP-EQM-001",
"problem_version": "1.0.0",
"target_weaknesses": [
"TOTAL_MOLES",
"MOLE_FRACTIONS",
"PARTIAL_PRESSURES",
"KP_EXPRESSION"
],
"variation_axes": [],
"review_status": "AI_DRAFT",
"note": "Self-reference is a fixture placeholder; selection claims remain unavailable until a reviewed multi-problem bank exists."
}
]
}