Chapter 8 Section 1.1

Chapter 8 Section 1.1

Introduction to Chemical Equations

​Introduction

• ​Chemical Reaction: The process by which one or more substances are changed into one or more different substances

  • ​Two components

    • ​Reactants: the original substances before the reaction takes place

    • ​Products: the resulting substances after the reaction takes place

  • ​According to the law of conservation of mass: the total mass of reactants must equal the total mass of the products

Draw

Circle the reactants in the chemical reaction $$\left(NH_4\right)_2Cr_2O_{7\left(s\right)}\rightarrow N_2+Cr_2O_{3\left(s\right)}+4H_2O_{\left(g\right)}$$  

Draw

Circle the products in the chemical reaction $$\left(NH_4\right)_2Cr_2O_{7\left(s\right)}\rightarrow N_2+Cr_2O_{3\left(s\right)}+4H_2O_{\left(g\right)}$$  

​Indications of a chemical reaction

• ​Sometimes it can be hard to tell if a chemical reaction has taken place, but there are indicators that can help us know if one has occurred

  • Release of energy as heat and light

    • ​Usually shows a chemical reaction, but not always

  • ​Production of a gas

  • ​Formation of a precipitate

    • ​Precipitate: A solid substance that results from the mixing of two dissolved liquids

  • ​A color change

​Characteristics of Chemical Equations

• ​A properly written chemical equation can summarize any chemical change

• ​Required information

  • ​The equation must represent all known facts: all reactants and products must be known

  • ​The equation must contain the correct formulas for the reactants and products: Make sure you keep track of diatomic molecules (see table 1 on page 263)

  • ​The law of conservation of Mass must be satisfied: Atoms can not be created or destroyed, so the same number of each must appear on both sides of the equation

​Using Word Equations and Formula Equations

Multiple Choice

How many more moles of hydrogen do we need on the products side of the equation to balance out the equation

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Multiple Choice

How many more moles of Oxygen do we need on the reactants side to have a balanced equation?

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