Chemical equation
H₂ + O₂ → H₂O Balanced Equation
The H2 O2 H2O balanced equation is 2H₂ + O₂ → 2H₂O. Hydrogen gas reacts with oxygen gas to form water, and the smallest whole-number coefficient ratio is 2 : 1 : 2.
Quick answer
Start with and balance it by placing 2 before H₂O, then 2 before H₂.
| Coefficients | 2 : 1 : 2 |
|---|---|
| Mole ratio | 2 : 1 : 2 |
| Reaction type | Synthesis / Combination |
Balanced Equation for H₂ + O₂ → H₂O
The coefficient table shows why the balanced hydrogen oxygen water equation uses the ratio 2 : 1 : 2.
Balanced equation
| Substance | Coefficient |
|---|---|
| H₂ | 2 |
| O₂ | 1 |
| H₂O | 2 |
Read the balanced equation as: 2 molecules or moles of H₂ react with 1 molecule or mole of O₂ to produce 2 molecules or moles of H₂O. In many homework answers, the same equation may be written as 2H2 + O2 = 2H2O.
How to Balance H₂ + O₂ → H₂O
Balance atoms by changing coefficients only. Do not change subscripts such as the 2 in H₂ or the 2 in O₂.
Step 1
Start with the unbalanced equation
H₂ + O₂ → H₂O
Step 2
Balance oxygen
O₂ has 2 oxygen atoms on the left, but H₂O has 1 oxygen atom on the right. Put 2 before H₂O: H₂ + O₂ → 2H₂O.
Step 3
Balance hydrogen
2H₂O contains 4 hydrogen atoms. Each H₂ has 2 hydrogen atoms, so put 2 before H₂: 2H₂ + O₂ → 2H₂O.
Step 4
Check the atom count
Reactants and products now both contain 4 H atoms and 2 O atoms.
After oxygen and hydrogen are both balanced, the final H2 + O2 balanced equation answer is 2H₂ + O₂ → 2H₂O.
Hydrogen + Oxygen → Water Equation
The same reaction can be written as a word equation or as a balanced chemical equation of water formation.
Word equation
Hydrogen + Oxygen → Water
Chemical equation
Whether the question is written as hydrogen oxygen equation, hydrogen oxygen water equation, or balanced chemical equation of water, the result is the same: hydrogen and oxygen combine to make water in the balanced ratio 2 : 1 : 2.
H₂ + O₂ → H₂O Mole Ratio
Balanced coefficients become the mole ratio used in stoichiometry.
Mole ratio
H₂ : O₂ : H₂O = 2 : 1 : 2
Two moles of H₂ react with one mole of O₂ to produce two moles of H₂O. A quick stoichiometry example is therefore:
2 mol H₂ + 1 mol O₂ → 2 mol H₂O
4 mol H₂ needs 2 mol O₂ and forms 4 mol H₂O.
Calculate grams, moles, or product amounts for this reaction in the stoichiometry calculator.
What Type of Reaction Is H₂ + O₂ → H₂O?
H₂ + O₂ → H₂O is a synthesis, or combination, reaction because two reactants combine to form one compound.
| Reaction type | Synthesis / combination |
|---|---|
| Pattern | A + B → AB |
| Also described as | Hydrogen combustion |
In the unbalanced formula, H₂ and O₂ are separate reactants. In the product, they are combined into H₂O, so the reaction follows the pattern A + B → AB.
It can also be described as the combustion of hydrogen in oxygen. For homework and stoichiometry problems, the key pieces are the balanced equation, the atom check, and the 2 : 1 : 2 mole ratio.
Atom Conservation Check for 2H₂ + O₂ → 2H₂O
A balanced equation conserves the number of atoms of each element on both sides of the arrow. That is why 2H₂ + O₂ → 2H₂O is balanced.
| Element | Reactants | Products | Balanced? |
|---|---|---|---|
| H | 4 | 4 | ✓ |
| O | 2 | 2 | ✓ |
The reactant side has 4 hydrogen atoms and 2 oxygen atoms. The product side has the same counts in 2H₂O, so both hydrogen and oxygen are conserved.
Reactants and Product
Identify each formula before using the equation in a mole-ratio, limiting-reactant, or theoretical-yield calculation.
| Side | Formula | Name |
|---|---|---|
| Reactant | Hydrogen | |
| Reactant | Oxygen | |
| Product | Water |
Related topics: H₂O molar mass · H₂O Lewis structure
Use This Equation in Chemistry Calculators
Once the equation is balanced, you can use it to work with specific amounts of H₂, O₂, or H₂O.
If hydrogen and oxygen are not supplied in a 2 : 1 mole ratio, one reactant will limit the amount of H₂O that can form. For example, with 1 mol H₂ and 1 mol O₂, hydrogen is limiting because the balanced equation requires twice as much H₂ as O₂.
Need an H2 O2 H2O balanced equation calculator? Use the Chemical Equation Balancer for this reaction, or calculate the maximum theoretical yield of water from a known amount of hydrogen or oxygen.
- Use in Stoichiometry CalculatorConvert between H₂, O₂, and H₂O using the 2 : 1 : 2 mole ratio.
- Find Limiting ReactantCheck whether hydrogen or oxygen runs out first for your amounts.
- Calculate Theoretical YieldEstimate the maximum water that can form from a known reactant amount.
- Balance Another Chemical EquationUse the equation balancer for any other reaction.
Related Chemical Equations
Browse nearby balanced-equation examples: synthesis, neutralization, and combustion reactions.
Frequently Asked Questions
What is the balanced equation for H2 + O2 → H2O?
The balanced equation is 2H₂ + O₂ → 2H₂O. The smallest whole-number coefficients are 2 for H₂, 1 for O₂, and 2 for H₂O.
What are the coefficients for H2 + O2 → H2O?
The coefficients are 2 : 1 : 2. That means 2H₂ + O₂ → 2H₂O, with an implied coefficient of 1 before O₂.
How do you balance H2 + O2 → H2O?
Balance oxygen first by placing 2 before H₂O. That gives two oxygen atoms on the product side. Then 2H₂O contains four hydrogen atoms, so place 2 before H₂ to get 2H₂ + O₂ → 2H₂O.
What is the hydrogen and oxygen water equation?
The word equation is hydrogen + oxygen → water. The balanced chemical equation is 2H₂ + O₂ → 2H₂O.
What is the mole ratio of H2 to O2?
The mole ratio of H₂ to O₂ is 2 : 1. Two moles of hydrogen gas react with one mole of oxygen gas.
What type of reaction is H2 + O2 → H2O?
H₂ + O₂ → H₂O is a synthesis, or combination, reaction because hydrogen and oxygen combine to form water. It can also be described as the combustion of hydrogen in oxygen.