Chemical Equations

Aim CE1aWhat does the chemical equation for photosynthesis tell us?

Chemical Reactions

• A chemical change that occurs, producing new arrangements of elements and compounds

Chemical Equations

• A short hand version of chemical reactions

• Each substance in the reaction is represented by chemical formulas

• An arrow ( ) shows the direction of the reaction

• Substances on the left side are generally reactants (your chemical “ingredients”)

• Substances on the right side are generally products (what you made)

Parts of a Chemical Equation

•Chemical formulaso The abbreviations for the elements or

compounds in the reaction

•Subscripts are in many chemical formulaso They show the number of atoms in each

substance

•Coefficients are in the chemical equationo They show the number of atoms, ions, or

molecules of each type in the reaction

A Visual of a Chemical Equation

coefficients Products

2 H2O(g) + O2(g) 2H2O(g) Reactants chemical

yield sign

phase symbolsQuestion: what is the coefficient of oxygen?Question: how many hydrogen atoms are on

the left and right of the reaction?

Example of a chemical reaction and its equation:

•What is the chemical equation for the Gummy Bear Demo, the heating of solid potassium chlorate which produces the oxygen gas and solid potassium chloride?

•Written out form: Solid potassium chlorate yields oxygen gas and solid potassium chloride

•Chemical Equation form: KClO3(s) O2(g) + KCl (s)

Try these:

•Solid Sodium metal and chlorine gas yield solid sodium chloride

•Chemical Equation form:

Na(s) + Cl2(g) NaCl(s)

• Aluminum metal and aqueous copper II chloride yield aqueous aluminum chloride and copper metal

•Chemical Equation form:

Al(s) + CuCl2(aq) AlCl3(aq) +Cu(s)

Balancing Chemical Equations

• In the reaction, Na(s) + Cl2(g) NaCl(s) , the Law of Conservation of Matter is broken… Why?

•The number of atoms of each element on the left does not equal the number of atoms on the right

•The reaction is not balanced

•Balancing is done be adding coefficients to the front of each substance in order to increase the number of atoms or molecules of each type in the equation

Balance the following equations:

1. ___ Na(s) + ___ Cl2(g) ___ NaCl(s)

2. ___ H2O(g) ___ H2(g) + ___ O2(g)

3. __Al(s) + __CuCl2(aq) __AlCl3(aq) +__Cu(s)