Stoichiometry Calculator

Calculate reactant and product quantities in chemical reactions using stoichiometric ratios and balanced equations.

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Advanced Stoichiometry Calculator

Calculate reactant and product quantities in chemical reactions with complete analysis, yield calculations, and comprehensive reaction insights.

Calculation Type

Balanced Chemical Equation

aA + bB → cC + dD (set coefficient to 0 if compound not present)

Molecular Weights (g/mol)

Results & Analysis

⚖️
Enter values and click calculate to see comprehensive stoichiometric analysis

Key Concepts

  • • Balanced equations show mole ratios
  • • 1 mole = 6.022 × 10²³ particles
  • • 1 mole gas = 22.4 L at STP
  • • 1 mole gas = 24.5 L at SATP

Common Molecular Weights

H₂O: 18.02
CO₂: 44.01
O₂: 31.98
N₂: 28.01
CH₄: 16.04
NaCl: 58.44

Conversion Factors

STP: 273.15 K, 1 atm
SATP: 298.15 K, 1 bar
Avogadro: 6.022 × 10²³
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About the Stoichiometry Calculator

Our advanced stoichiometry calculator is a comprehensive tool for chemical calculations that handles basic stoichiometry, limiting reagent analysis, percent yield calculations, and empirical formula determination. It provides detailed step-by-step solutions with complete unit conversions and comprehensive reaction analysis.

This calculator supports custom reactions and common preset equations, making it perfect for students learning stoichiometry concepts and professionals performing quantitative chemical analysis. It includes automatic molecular weight lookup, molar ratio calculations, and visual representation of results.

Stoichiometry Formulas

Basic Stoichiometry

\[ \text{moles} = \frac{\text{mass (g)}}{\text{molecular weight (g/mol)}} \]
\[ \text{Molar ratio} = \frac{\text{coefficient A}}{\text{coefficient B}} \]

Limiting Reagent

\[ \text{Theoretical yield} = \text{limiting reagent moles} \times \text{stoichiometric ratio} \]
\[ \text{Compare: } \frac{\text{moles A}}{\text{coeff A}} \text{ vs } \frac{\text{moles B}}{\text{coeff B}} \]

Percent Yield

\[ \% \text{ Yield} = \frac{\text{actual yield}}{\text{theoretical yield}} \times 100\% \]

Unit Conversions

\[ \text{Molecules} = \text{moles} \times 6.022 \times 10^{23} \]
\[ \text{Volume (STP)} = \text{moles} \times 22.4 \text{ L} \]
\[ \text{Volume (SATP)} = \text{moles} \times 24.5 \text{ L} \]

How to Use This Calculator

Step-by-Step Guide

  1. Select Calculation Type: Choose basic stoichiometry, limiting reagent, or percent yield
  2. Enter Reaction: Use preset reactions or enter custom coefficients
  3. Add Molecular Weights: Enter molecular weights for accurate mass calculations
  4. Input Known Quantities: Enter the amount and unit of known substance
  5. Calculate: Click calculate to get comprehensive analysis
  6. Analyze Results: Review molar ratios, yields, and unit conversions

Pro Tips

  • Always start with a balanced chemical equation
  • Use accurate molecular weights for precise calculations
  • For limiting reagent, enter amounts of all reactants
  • Check molar ratios to verify your balanced equation
  • Consider significant figures in your final answers
  • Use STP (273.15 K, 1 atm) or SATP (298.15 K, 1 bar) conditions appropriately

Worked Examples

Example 1: Basic Stoichiometry

Given:

  • • Reaction: 2H₂ + O₂ → 2H₂O
  • • Amount of H₂: 4.0 g
  • • Find: moles of H₂O produced
  • • MW(H₂) = 2.02 g/mol

Solution:

Moles H₂ = 4.0 g ÷ 2.02 g/mol = 1.98 mol
Molar ratio H₂:H₂O = 2:2 = 1:1
Moles H₂O = 1.98 mol H₂ × (2 mol H₂O / 2 mol H₂)
Moles H₂O = 1.98 mol

Example 2: Limiting Reagent

Given:

  • • Reaction: N₂ + 3H₂ → 2NH₃
  • • N₂: 2.0 mol available
  • • H₂: 4.0 mol available
  • • Find: limiting reagent

Solution:

From N₂: 2.0 mol ÷ 1 = 2.0 mol NH₃ possible
From H₂: 4.0 mol ÷ 3 = 1.33 mol NH₃ possible
H₂ produces less NH₃
Limiting reagent: H₂
NH₃ produced: 2.67 mol

Example 3: Percent Yield

Given:

  • • Theoretical yield: 25.0 g
  • • Actual yield: 21.3 g
  • • Find: percent yield

Solution:

% Yield = (Actual ÷ Theoretical) × 100%
% Yield = (21.3 g ÷ 25.0 g) × 100%
% Yield = 85.2%
Category: Good

Understanding Your Results

Stoichiometric Relationships

Molar Ratios
Coefficients in balanced equations show mole relationships
Limiting Reagent
Reactant that is completely consumed first
Excess Reagent
Reactant that remains after reaction completion
Theoretical Yield
Maximum possible product based on stoichiometry

Yield Categories

Excellent (≥90%)
Very high efficiency, minimal side reactions
Good (70-89%)
Acceptable efficiency for most applications
Fair (50-69%)
Some optimization needed
Poor (<50%)
Significant optimization required

Frequently Asked Questions

How do I identify the limiting reagent?

Calculate how much product each reactant can produce. The reactant that produces the least amount of product is the limiting reagent.

Why is my percent yield over 100%?

This suggests experimental error, impure products, or side reactions producing additional products. Check your measurements and reaction conditions.

What causes low percent yields?

Incomplete reactions, side reactions, product loss during purification, measurement errors, or reversible reactions can all reduce yield.

How do I balance chemical equations?

Start with the most complex molecule, balance atoms one at a time, and adjust coefficients to make equal numbers of each atom on both sides.

Applications & Use Cases

🎓

Education

  • • Chemistry coursework
  • • Laboratory calculations
  • • Homework problems
  • • Exam preparation
🏭

Industrial

  • • Process optimization
  • • Batch calculations
  • • Cost analysis
  • • Quality control
🔬

Research

  • • Synthesis planning
  • • Yield optimization
  • • Reaction analysis
  • • Method development

Limitations & Considerations

Important Notes

  • Balanced Equations: Calculations assume perfectly balanced chemical equations
  • Complete Reactions: Assumes reactions go to completion (not always true)
  • Side Reactions: Does not account for competing reactions or byproducts
  • Ideal Conditions: Assumes standard temperature and pressure when using gas volumes
  • Purity: Assumes 100% pure reactants and products
  • Measurement Errors: Results depend on accuracy of input measurements
  • Equilibrium: Does not apply to equilibrium reactions (use ICE tables instead)
  • Significant Figures: Results shown with high precision; round according to data quality
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