NO + O2 = NO2 - Balanced Chemical Equation

NO + O2 = NO2 - Balanced Chemical Equation

Use the calculator below to balance chemical equations and determine the type of reaction (instructions).

Balanced Chemical Equation

2NO + O2 → 2NO2
⬇ Scroll down to see reaction info and a step-by-step answer, or balance another equation.

Reaction Information

Word Equation

Nitric Oxide (Radical) + Dioxygen = Nitrogen Dioxide

NO + O2 = NO2 is a Synthesis reaction where two moles of Nitric Oxide (Radical) [NO] and one mole of Dioxygen [O2] combine to form two moles of Nitrogen Dioxide [NO2]

Structure of NO + O2 = NO2

Reaction Type

Synthesis

  • Redox

Redox (Oxidation-Reduction) Reaction

NO + O2 = NO2 might be a redox reaction.

Reactants

Products

Thermodynamics

Thermodynamics of the reaction can be calculated using a lookup table.

No state of matter options are available for this reaction.

Is the Reaction Exothermic or Endothermic?

NO (g)2 mol90.24888 kJ/mol-180.49776 kJ
O2 (g)1 mol0 kJ/mol-0 kJ
NO2 (g)2 mol33.17912 kJ/mol66.35824 kJ
ΣΔH°f(reactants)180.49776 kJ
ΣΔH°f(products)66.35824 kJ
ΔH°rxn-114.13952 kJ
ΣΔH°f(reactants) > ΣΔH°f(products), so NO + O2 = NO2 is exothermic (releases heat).

Is the Reaction Exoentropic or Endoentropic?

ΔS = Sproducts - Sreactants. If ΔS < 0, it is exoentropic. If ΔS > 0, it is endoentropic.

NO (g)2 mol210.651848 J/(mol K)-421.303696 J/K
O2 (g)1 mol205.028552 J/(mol K)-205.028552 J/K
NO2 (g)2 mol239.9524 J/(mol K)479.9048 J/K
ΣΔS°(reactants)626.332248 J/K
ΣΔS°(products)479.9048 J/K
ΔS°rxn-146.427448 J/K
ΣΔS°(reactants) > ΣΔS°(products), so NO + O2 = NO2 is exoentropic (decrease in entropy).

Is the Reaction Exergonic or Endergonic?

ΔG = Gproducts - Greactants. If ΔG < 0, it is exergonic. If ΔG > 0, it is endergonic.

NO (g)2 mol86.56696 kJ/mol-173.13392 kJ
O2 (g)1 mol0 kJ/mol-0 kJ
NO2 (g)2 mol51.29584 kJ/mol102.59168 kJ
ΣΔG°(reactants)173.13392 kJ
ΣΔG°(products)102.59168 kJ
ΔG°rxn-70.54224 kJ
ΣΔG°(reactants) > ΣΔG°(products), so NO + O2 = NO2 is exergonic (releases energy).

Reaction Expressions

Kc or Q = ( [NO2]2 ) / ( [NO]2 [O2] )
(assuming all reactants and products are aqueous. substitutue 1 for any solids/liquids, and Psubstance for gases.)
rate = -1/2 * (Δ[NO] / Δt) = -(Δ[O2] / Δt) = 1/2 * (Δ[NO2] / Δt)
(assuming constant volume in a closed system and no accumulation of intermediates or side products)
Calculate Reaction Stoichiometry
Calculate Limiting Reagent

Balance NO + O2 = NO2 Using the Algebraic Method

How To Balance NO + O2 = NO2

To balance the equation NO + O2 = NO2 using the algebraic method step-by-step, you must have experience solving systems of linear equations. The most common methods are substitution/elimination and linear algebra, but any similar method will work.

Step 1: Label Each Compound With a Variable

Label each compound (reactant or product) in the equation with a variable to represent the unknown coefficients.

a NO + b O2 = c NO2

Step 2: Create a System of Equations

Create an equation for each element (N, O) where each term represents the number of atoms of the element in each reactant or product.

N:	1a	+	0b	=	1c
O:	1a	+	2b	=	2c

Step 3: Solve For All Variables

Use substitution, Gaussian elimination, or a calculator to solve for each variable.

  • 1a - 1c = 0
  • 1a + 2b - 2c = 0

Use your graphing calculator's rref() function (or an online rref calculator) to convert the following matrix into reduced row-echelon-form:

[ 1	 0	-1	0]
[ 1	 2	-2	0]
The resulting matrix can be used to determine the coefficients. In the case of a single solution, the last column of the matrix will contain the coefficients.

Simplify the result to get the lowest, whole integer values.

  • a = 2 (NO)
  • b = 1 (O2)
  • c = 2 (NO2)

Step 4: Substitute Coefficients and Verify Result

Count the number of atoms of each element on each side of the equation and verify that all elements and electrons (if there are charges/ions) are balanced.

2 NO + O2 = 2 NO2
Reactants Products
N22✔️
O44✔️
Since there is an equal number of each element in the reactants and products of 2NO + O2 = 2NO2, the equation is balanced.

Balance NO + O2 = NO2 Using Inspection

The law of conservation of mass states that matter cannot be created or destroyed, which means there must be the same number atoms at the end of a chemical reaction as at the beginning. To be balanced, every element in NO + O2 = NO2 must have the same number of atoms on each side of the equation. When using the inspection method (also known as the trial-and-error method), this principle is used to balance one element at a time until both sides are equal and the chemical equation is balanced.

Step 1: Count the number of each element on the left and right hand sides

Reactants (Left Hand Side)Products (Right Hand Side)
ReactantsProducts
NOO2TotalNO2Total
N1111✔️
O12322❌

Step 2: Multiply coefficients for compounds to balance out each element

For each element that is not equal, try to balance it by adding more of it to the side with less. Sometimes there may be multiple compounds with that element on one side, so you'll need to use your best judgement and be prepared to go back and try the other options.

  1. O is not balanced. Add 1 molecule of NO2 to the product (right-hand) side to try to balance Oxygen:
    NO + O2 = 2NO2
    ReactantsProducts
    N12❌
    O34❌
  2. N is not balanced. Add 1 molecule of NO to the reactant (left-hand) side to balance Nitrogen:
    2NO + O2 = 2NO2
    ReactantsProducts
    N22✔️
    O44✔️

Step 3: Verify that the equation is balanced

Since there are an equal number of atoms of each element on both sides, the equation is balanced.

2NO + O2 = 2NO2

Practice Balancing

+
=
ReactantsProducts
N11✔️
O32❌
Hint: The sum of coefficients is 5. See Step-By-Step Solution

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Instructions

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  • Use uppercase for the first character in the element and lowercase for the second character. Examples: Fe, Au, Co, Br, C, O, N, F.
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