{
    "name": "Limiting Reagent Calculator",
    "url": "https://calculators.geekmidst.com/calculators/limiting-reagent-calculator",
    "markdown": "https://calculators.geekmidst.com/calculators/limiting-reagent-calculator.md",
    "category": "Science & engineering",
    "description": "Find which reactant runs out first in aA + bB → cP, the theoretical yield of product in grams and how much of the excess reactant is left over.",
    "summary": "Divide each reactant’s moles by its coefficient in the balanced equation. The smaller result is the limiting reagent, and it sets how much product can form.",
    "also_called": [
        "Limiting reactant calculator",
        "Stoichiometry calculator",
        "Theoretical yield calculator"
    ],
    "applies_to": "Worldwide",
    "last_updated": "2026-10-29",
    "computation": "Results are computed in the visitor’s browser on the HTML page. This API describes the calculator; it does not compute results.",
    "inputs": [
        {
            "name": "a_name",
            "label": "Reactant A name",
            "type": "text",
            "default": "H2"
        },
        {
            "name": "a_mass",
            "label": "Mass of A",
            "type": "number",
            "default": "10",
            "unit": "g"
        },
        {
            "name": "a_molar_mass",
            "label": "Molar mass of A",
            "type": "number",
            "default": "2.016",
            "unit": "g/mol"
        },
        {
            "name": "a_coef",
            "label": "Coefficient of A (a)",
            "type": "number",
            "default": "2"
        },
        {
            "name": "b_name",
            "label": "Reactant B name",
            "type": "text",
            "default": "O2"
        },
        {
            "name": "b_mass",
            "label": "Mass of B",
            "type": "number",
            "default": "64",
            "unit": "g"
        },
        {
            "name": "b_molar_mass",
            "label": "Molar mass of B",
            "type": "number",
            "default": "31.998",
            "unit": "g/mol"
        },
        {
            "name": "b_coef",
            "label": "Coefficient of B (b)",
            "type": "number",
            "default": "1"
        },
        {
            "name": "p_coef",
            "label": "Coefficient of the product (c)",
            "type": "number",
            "default": "2"
        },
        {
            "name": "p_molar_mass",
            "label": "Molar mass of the product",
            "type": "number",
            "default": "18.015",
            "unit": "g/mol"
        }
    ],
    "outputs": [
        {
            "key": "limiting",
            "label": "Limiting reagent",
            "format": "text"
        },
        {
            "key": "yield_g",
            "label": "Theoretical yield of product",
            "format": "number"
        },
        {
            "key": "product_mol",
            "label": "Product formed",
            "format": "number"
        },
        {
            "key": "excess_left_g",
            "label": "Excess reactant left over",
            "format": "number"
        },
        {
            "key": "a_mol",
            "label": "Moles of A",
            "format": "number"
        },
        {
            "key": "b_mol",
            "label": "Moles of B",
            "format": "number"
        }
    ],
    "formula": {
        "text": "n = m ÷ M;  limiting = smaller of n_A ÷ a and n_B ÷ b;  product = c × min(n_A/a, n_B/b);  yield = product × M_P",
        "variables": {
            "a, b, c": "coefficients in the balanced equation aA + bB → cP",
            "n_A, n_B": "moles of each reactant",
            "M_P": "molar mass of the product"
        }
    },
    "worked_example": {
        "inputs": {
            "a_name": "H2",
            "a_mass": "10",
            "a_molar_mass": "2.016",
            "a_coef": "2",
            "b_name": "O2",
            "b_mass": "64",
            "b_molar_mass": "31.998",
            "b_coef": "1",
            "p_coef": "2",
            "p_molar_mass": "18.015"
        },
        "steps": [
            "n(H₂) = 10 ÷ 2.016 = 4.9603 mol → ÷ 2 = 2.4802; n(O₂) = 64 ÷ 31.998 = 2.0001 mol → ÷ 1 = 2.0001.",
            "O₂ gives the smaller ratio, so it is limiting: water = 2 × 2.000125 = 4.00025 mol × 18.015 = 72.06 g.",
            "H₂ used = 4.00025 mol × 2.016 = 8.0645 g, so 10 − 8.0645 = 1.94 g of H₂ is left."
        ],
        "result": "In 2H₂ + O₂ → 2H₂O with 10 g H₂ and 64 g O₂, oxygen is limiting; at most 72.06 g of water forms and 1.94 g of hydrogen is left over."
    },
    "interpretation": "Actual yield is usually lower than theoretical; percentage yield = actual ÷ theoretical × 100.",
    "assumptions": [
        "The equation is balanced and the reaction goes to completion.",
        "Reactants are pure."
    ],
    "limitations": [
        "Two reactants and one product of interest; for more reactants, compare every n ÷ coefficient ratio the same way."
    ],
    "rules": null,
    "faqs": [
        {
            "question": "Is the reactant with the smaller mass always limiting?",
            "answer": "No. Compare moles divided by coefficients, not grams. Here 10 g of hydrogen is in excess over 64 g of oxygen."
        },
        {
            "question": "Can I use fractional coefficients?",
            "answer": "Yes. Only the ratios between coefficients matter."
        }
    ],
    "sources": [],
    "related": [
        {
            "name": "Mole to Mass Calculator",
            "url": "https://calculators.geekmidst.com/calculators/mole-to-mass-calculator"
        },
        {
            "name": "Molecular Weight Calculator",
            "url": "https://calculators.geekmidst.com/calculators/molecular-weight-calculator"
        },
        {
            "name": "Molarity Calculator",
            "url": "https://calculators.geekmidst.com/calculators/molarity-calculator"
        }
    ],
    "disclaimer": null,
    "publisher": "GM¹X CalcVerse"
}