Lesson 11 Classifying Chemical Reactions
Completion requirements
Types of Chemical Reaction Equations
What are the three different ways that chemical reactions can be written?
B11.6 Chemical reaction equation
Most often, you will use balanced chemical reaction equations. On occasion, other types of chemical reaction equations—word equations and skeleton equations—will be used. Each type of reaction equation conveys slightly different information.
A word equation is a way of organizing and displaying information about a chemical change. It is a gateway to eventually writing a balanced chemical reaction equation.
For example, a piece of zinc metal is dropped into a beaker of hydrobromic acid to produce aqueous zinc bromide and bubbles of hydrogen gas.
Reactants are the entities that are used to start the chemical reaction. They are separated by a plus sign. An arrow is used to separate the reactants from the products. A key term in this example is “to produce,” which indicates which entities are the products.
zinc + hydrobromic acid → zinc bromide + hydrogen
The reactants—zinc and hydrobromic acid—could have been written in any order and still be correct. The same goes for the products.
For example, a piece of zinc metal is dropped into a beaker of hydrobromic acid to produce aqueous zinc bromide and bubbles of hydrogen gas.
Reactants are the entities that are used to start the chemical reaction. They are separated by a plus sign. An arrow is used to separate the reactants from the products. A key term in this example is “to produce,” which indicates which entities are the products.
zinc + hydrobromic acid → zinc bromide + hydrogen
The reactants—zinc and hydrobromic acid—could have been written in any order and still be correct. The same goes for the products.
A skeleton equation shows the formulas of the reactants and products, but it does not show the correct proportions of either—no coefficients are added into a skeleton equation. You will need to recall the guidelines for writing chemical formulas from Section 2.
For the example above, the skeleton equation is
Zn(s) + HBr(aq) → ZnBr2(aq) + H2(g)
For the example above, the skeleton equation is
Zn(s) + HBr(aq) → ZnBr2(aq) + H2(g)
B11.7 Chemical reaction
B11.8 Balancing
Recall from previous science courses that the law of conservations of mass states that the total mass of reactants must equal the total mass of products. This law is used to balance chemical reaction equations by ensuring the number of atoms of each element is the same on the reactant side and the product side. You will learn how to balance chemical reaction equations in the next lesson. The balanced equation for the above example would be
Zn(s) + 2HBr(aq) → ZnBr2(aq) + H2(g)
Zn(s) + 2HBr(aq) → ZnBr2(aq) + H2(g)
Read This
Please read pages 86 to 88 in your Science 10 textbook. Make sure you take notes on your readings to study from later. You should focus on the three ways that chemical reaction information can be displayed. Remember, if you have any questions or you do not understand something, ask your teacher! Practice Questions
Complete the following practice question to check your understanding of the concept you just learned. Make sure you write a complete answer to the practice
question in your notes. After you have checked your answer, make corrections to your response (where necessary) to study from.- When a solid strip of magnesium is ignited, it reacts with oxygen gas from the air to produce solid magnesium oxide. Write the word equation and a skeleton equation for the described reaction.
Word equation:
magnesium + oxygen → magnesium oxide
Skeleton equation:
Mg(s) + O2(g) → MgO(s)
- Aqueous solutions of barium chloride and potassium hydroxide react to produce solid barium hydroxide and aqueous potassium chloride. Write the word equation and a skeleton equation for the described reaction.
Word equation:
barium chloride + potassium hydroxide → barium hydroxide + potassium chloride
Skeleton equation:
BaCl2(aq) + KOH(aq) → Ba(OH)2(s) + KCl(aq)