Writing Chemical Equations

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Describing Chemical Reactions

> Writing Chemical Equations

Word Equations

To write a word equation, write the names of the reactants to the left of the arrow separated by plus signs; write the names of the products to the right of the arrow, also separated by plus signs.

Reactant + Reactant Product + Product

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Methane + Oxygen Carbon dioxide + Water

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iron + oxygen iron(III) oxide

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Hydrogen Peroxide Water and Oxygen

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Chemical Equations

A chemical equation is a representation of a chemical reaction; the formulas of the reactants (on the left) are connected by an arrow with the formulas of the products (on the right).

Na + Cl NaCl

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Skeletal Formulas

Write the formulas of the reactants to the left of the yields sign (arrow) and the formulas of the products to the right.

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A skeleton equation is a chemical equation that does not indicate the relative amounts of the reactants and products.

Here is the equation for rusting:

Fe + O2 Fe2O3

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A catalyst is a substance that speeds up the reaction but is not used up in the reaction.

Without Catalyst With Catalyst

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> Writing Chemical Equations11.1


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Animation 12

Relate chemical symbols and formulas to the information they communicate.



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Balancing Chemical Equations

Balancing Chemical Equations

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> Balancing Chemical Equations

To write a balanced chemical equation, first write the skeleton equation. Then use coefficients to balance the equation so that it obeys the law of conservation of mass.

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This is a balanced equation for making a bicycle. The numbers are called coefficients—small whole numbers that are placed in front of the formulas in an equation in order to balance it.

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A chemical reaction is also described by a balanced equation in which each side of the equation has the same number of atoms of each element and mass is conserved.

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Simulation 11

Sharpen your skills by balancing chemical equations.

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Writing Chemical Equations