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Chemical Equations Worksheet 1.1 D. Crosby

Name: __________________________    Class: _______

Chemical Equations are the chemist' shorthand. They tell at a glance what substances have been mixed together and what new substance(s) have been produced. Chemical equations are useful to the chemist because they represent chemical reactions. Scientists use chemical reactions to show how various elements and compounds react.

The substance or substances that are the starting materials in a chemical reaction are called reactants and are located on the left side of the equation. The substance or substances produced as the result of a reaction are called products and are located on the right side of the chemical equation.

Hydrogen gas and oxygen gas react to produce water. The chemical equation for this reaction is:

2H2 + O2 2 H2O


  1. Identify the symbol(s) representing the reactant(s): _________________________________________
  2. Identify the symbol(s) representing the product(s): ______________________________________
  3. Some reactions require continuing energy in order to occur. Some reactions occur spontaneously when the reactants are mixed together. Other reactions just need energy to get started and will then continue until one or more reactants are used up. The following are examples of two types of chemical reactions. The equation 2H2 + O2 2 H2O represents a synthesis reaction because two or more different reactants combine to form a single product. The equation 2H3PO4 H4P2O7 + H2O represents a decomposition reaction because a single reactant is decomposed to form two or more different products.

  4. The equation 2H2O2 2H2O + O2 represents what type of reaction? ___________________________
  5. Identify the reactant(s) and product(s) in the equation: _______________________________________
  6. Identify each of the following equations as either decomposition or synthesis reactions.

  7. 2C + 02 2CO _______________________________
  8. 2HgO 2 Hg + 02 ____________________________
  9. H2 + Cl2 2HCl ______________________________

The following equation represents a single displacement reaction. Mg + 2HCl MgCl2 = H2

In the reaction, the metal magnesium (Mg) has displaced the hydrogen atom (H) in HCl and formed magnesium chloride and hydrogen gas (H2) as products. In a single displacement reaction an element and a compound react to form another element and compound.

In contrast with the single displacement, the following equation is called a double displacement reaction; two compounds react to form two different compounds.

BaCl2 + Na2SO4 BaSO4 + 2 NaCl


In this reaction, the Ba displaces the Na in Na2SO4 to form BaSO4 . The Na displaces the Ba in BaCl2 to form NaCl. In the following examples, two substances react to form two different substances.

{8} 2KCl + 2HgNO3 2KNO3 + Hg2Cl2 What type of reaction is this? ____________________________

{9} 2Na + H2SO4 Na2SO4 + H2 What type of reaction is this? __________________________________

Identify the following reaction equations as synthesis, decomposition, single displacement, or double displacement.

10. 2KclO3 2KCl + 3O2 __________________________________________________

11. H2 + Cl2 2HCl __________________________________________________

12. Zn + Cu(NO3) 2 Cu + Zn(NO3) 2 __________________________________________________

13. AgNO3 + KCl AgCl + KNO3 __________________________________________________

14. FeCl3 + 3KOH Fe(OH) 3 + 3KCl __________________________________________________

Double displacement reactions are especially important because a large number of reactions are of this type. Think of double displacement reactions as compounds exchanging partners in a dance. In a double displacement reaction the metal, or NH4+, or H+ ion of one reactant replaces the metal, or NH4+, or H+ ion in the other reactant, and vice versa.

In the following generalized reaction equation, A nd B are positive ions (metals, NH4+, or H+) and X and Y are negative ions (one or more nonmetal atoms of an ionic compound which remain after the positive ion is removed.


In this equation, A has displaced B and B has displaced A. In the following double displacement reaction, the products can be predicted.

AgNO3 + NaCl ???


The positive metal ions are Ag+ and Na+. The negative ions are NO3- and Cl-. Predict the products of this reaction.

Predict the products of the following double displacement reactions.

15. CuSO4 + Ca(OH)2 ____________________________________________________

16. NaC2H3O2 + HCl _____________________________________________________