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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 à 2 H2O
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 à 2 H2O represents a synthesis reaction because two or more different reactants combine to form a single product. The equation
Identify each of the following equations as either decomposition or synthesis reactions.
The following equation represents a single displacement reaction.
Mg + 2HCl à MgCl2 = H2In 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.
BaCl
2 + Na2SO4 à 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 à 2KNO3 + Hg2Cl2 What type of reaction is this? ____________________________
{9} 2Na + H2SO4 à Na2SO4 + H2 What type of reaction is this? __________________________________
Identify the following reaction equations as synthesis, decomposition, single displacement, or double displacement.
10. 2KclO3 à 2KCl + 3O2 __________________________________________________
11. H2 + Cl2 à 2HCl __________________________________________________
12. Zn + Cu(NO3) 2 à Cu + Zn(NO3) 2 __________________________________________________
13. AgNO3 + KCl à AgCl + KNO3 __________________________________________________
14. FeCl3 + 3KOH à 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.
AX + BY à BX + AY
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 à ???
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 à ____________________________________________________
16. NaC2H3O2 + HCl à _____________________________________________________