Stoichiometry Calculator
The Stoichiometry Calculator uses mole ratios from balanced chemical equations to determine the amounts of reactants and products. Calculate theoretical yield, identify limiting reagents, and convert between moles, grams, and liters for any reaction.
🕐 Recent Calculations
What is Stoichiometry?
Stoichiometry is the calculation of quantities in chemical reactions based on balanced equations. The coefficients in a balanced equation give the mole ratio — for 2H₂ + O₂ → 2H₂O, the ratio is 2:1:2, meaning 2 moles of hydrogen react with 1 mole of oxygen to produce 2 moles of water.
Stoichiometric calculations are essential in chemistry for determining how much reagent is needed, predicting product yields, identifying limiting reagents, and calculating percent yield. The mole ratio is the bridge between reactants and products.
使用される計算公式・方程式
この計算ツールは5つの主要な公式を使用しています：
1 Mole Ratio Conversion ▼
For 2H₂ + O₂ → 2H₂O: 3 moles H₂ produces 3 × (2/2) = 3 moles H₂O.
2 Moles from Grams ▼
36 grams of water (H₂O, MW=18): Moles = 36 / 18 = 2 moles.
3 Theoretical Yield ▼
Determines the maximum possible product from the limiting reagent.
比率計算ツールの使い方
この比率計算ツールは、以下の3ステップで簡単にご利用いただけます：
数値を入力
入力欄に既知の比率の値を入力します。求めたい未知数の入力欄は空欄のままにしておきます。
モードを選択
比率モード（解く、簡素化、スケーリング）を選択します。各モードで異なる計算式が適用されます。
結果を確認
計算するボタンを押します。結果画面に答えと、視覚的な比率バー、円グラフ、詳細なステップバイステップの解決プロセスが表示されます。
実例問題と段階的な解説
本比率計算ツールを使って、以下の3つの例題をステップバイステップで解決するプロセスです：
入力 1 How much O₂ needed to react with 4 moles H₂?
入力 2 Theoretical yield from 10g CH₄ burning in excess O₂
入力 3 Find limiting reagent: 5 mol H₂ and 4 mol O₂
よくある質問 (FAQ)
What is a mole ratio? ▼
A mole ratio is the ratio of coefficients in a balanced equation. For N₂ + 3H₂ → 2NH₃, the mole ratios are N₂:H₂ = 1:3, H₂:NH₃ = 3:2, and N₂:NH₃ = 1:2.
What is a limiting reagent? ▼
The limiting reagent is the reactant that runs out first, determining the maximum product yield. The other reactant is 'in excess.' Identify it by dividing each reactant's moles by its coefficient — the smallest quotient is the limiting reagent.
How do you calculate percent yield? ▼
Percent Yield = (Actual Yield / Theoretical Yield) × 100. If you expected 50g of product but obtained 42g: Percent Yield = (42/50) × 100 = 84%.
Why must chemical equations be balanced for stoichiometry? ▼
Balanced equations obey the law of conservation of mass — atoms are neither created nor destroyed. Unbalanced equations give incorrect mole ratios and wrong calculations.
How do you convert between moles and grams? ▼
Multiply moles by molar mass to get grams. Divide grams by molar mass to get moles. Example: 3 moles of NaCl (MW=58.44) = 3 × 58.44 = 175.3 grams.