Chemical Equations and Mole Relationships

Mole ratios Example

Dr. Walt Volland revised October 12, 2009

The balanced equations are a chemists recipe for producing a product from reactants. The equation tell us the amounts of reactants needed and the amount of product formed. Balanced equations can be viewed at three levels. The first is the molecular level. The second is the mole level. The third is in terms of masses. We will look at mole relationships here. The next section deals with masses.
These interpretations of chemical equations are of value because they enable us to make predictions about the outcome of reactions.


Burning carbon and carbon containing compounds in air can produce carbon monoxide. This is one reason why carbon monoxide detectors are marketed for consumers. Space heaters have sometimes killed unsuspecting people. What they didn't know did hurt them. Carbon monoxide is poisonous. It is cumulative and even if it doesn't kill it can cause chronic illness and brain damage.


2 C(s) + O2(g) -----> 2 CO(g)


This equation can be viewed in terms of the atomic and molecular level. Two atoms of carbon must react with one molecule of oxygen. Two molecules of carbon monoxide are produced. return to top of page

The coefficients in the balanced equation tell the moles of each substance involved in the equation

The mole ratios for this equation are

2 moles C / 1 mole O2
2 moles C / 2 mole CO2

1 mole O2 / 2 moles C
2 moles CO2 / 2 mole C

These two ratios are really one to one.
1 mole O2 / 2 mole CO2

2 mole CO2 / 1 mole O2

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The reaction between nitrogen and oxygen to produce nitrogen dioxide is analyzed here.

The balanced equation is N2(g) + 2 O2(g)---> 2 NO2(g)

Exercise: What is the mol ratio for nitrogen to oxygen for the equation above?

Answer: 1 mole N2 : 2 moles O2

Dr. Walt Volland, , All rights reserved, 2009 return to top of page
last modified October 12, 2009