Stoichiometry is the section of chemistry that involves calculating the quantitative relationships between reactants and products in a balanced chemical reaction. It is based on the Law of Conservation of Mass, which states that matter cannot be created or destroyed. Therefore, the total mass of the reactants must equal the total mass of the products.
How to Use This Stoichiometry Calculator
This calculator performs mass-to-mass conversions, which is the most common stoichiometric calculation in laboratory settings. Follow these steps:
Balance the Equation: You must start with a balanced chemical equation to find the coefficients (the numbers in front of the molecules).
Identify Knowns: Enter the mass of the reactant or product you currently have.
Enter Molar Masses: Find the molar mass for both substances using a periodic table (e.g., O₂ = 32.00 g/mol).
Calculate: The tool will convert mass to moles, apply the mole ratio, and convert back to the target mass.
Realistic Example: Formation of Water
Equation: 2H₂ + 1O₂ → 2H₂O
If you have 10 grams of O₂ (Known), how much H₂O (Unknown) can you produce?
Mass Known: 10g
Molar Mass O₂: 32.00 g/mol
Coefficient O₂: 1
Coefficient H₂O: 2
Molar Mass H₂O: 18.02 g/mol
Result: 11.26 grams of H₂O.
Why Stoichiometry Matters
In industrial chemistry and pharmacy, stoichiometry is used to determine the exact amount of raw materials needed to create a specific amount of medicine or product. This minimizes waste (limiting reactants) and maximizes efficiency. It is also used in environmental science to calculate how much carbon dioxide is produced from burning a specific amount of fuel.
function calculateStoich() {
// Get values from inputs
var massK = parseFloat(document.getElementById('massKnown').value);
var mmK = parseFloat(document.getElementById('mmKnown').value);
var cK = parseFloat(document.getElementById('coeffKnown').value);
var cU = parseFloat(document.getElementById('coeffUnknown').value);
var mmU = parseFloat(document.getElementById('mmUnknown').value);
// Check for valid inputs
if (isNaN(massK) || isNaN(mmK) || isNaN(cK) || isNaN(cU) || isNaN(mmU) || mmK <= 0 || cK <= 0 || cU <= 0 || mmU Moles Known
var molesK = massK / mmK;
// 2. Use Mole Ratio: Moles Known * (Coeff Unknown / Coeff Known) -> Moles Unknown
var molesU = molesK * (cU / cK);
// 3. Convert Moles Unknown -> Mass Unknown
var massU = molesU * mmU;
// Display results
document.getElementById('molesKnownRes').innerHTML = molesK.toFixed(4);
document.getElementById('molesUnknownRes').innerHTML = molesU.toFixed(4);
document.getElementById('massUnknownRes').innerHTML = massU.toFixed(2);
// Show the result box
document.getElementById('stoichResult').style.display = 'block';
}