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Home Concept Builders Chemical Reactions Writing Balanced Chemical Equations Help Help 3

Writing Balanced Chemical Equations - Questions 3 Help

Chemical reactions involve changes - changes of reactants into products. Basic chemical reactions can be grouped into categories based on the types of changes that are occuring during the reaction. There are five basic categories - synthesis, decomposition, combustion, single replacement, and double replacement. If you know the type of reaction that reactants will involve themselves in, then you can predict the products that will be produced as the result of that reaction.

There are two questions in this Question Group. The two questions are very similar or are the same type of reaction The question below is one of the questions.
 

Version 1:
Aluminum and copper(II) sulfate undergo a single replacement reaction. Predict the formulae of the two products of the reaction.
 
Cu and AlSO4
Al2Cu3 and SO2
Cu and Al4(SO)3
Cu and Al2(SO4)3
Cu2 and Al2(SO4)3

To be successful with this question, you need to understand what a single replacement reaction is and how to write formulas for ionic compounds.

A single replacement reaction involves the reaction of an element with a compound (most often an ionic compound). The single element replaces one of the ions in the compound. If the reactant that is an element is a metal, then it will replace the cation (positive ion) that is present in the reactant that is an ionic compound. A new ionic compound is thus formed as a product and the other product is an element - the elemental form of the cation from the original ionic compound. The generic equation for such a reaction is ...
 
A + BC ==> AC + B (if A is a metal)

A + BC ==> BA + C (if A is a non-metal)
 
Here A, B, and C are fictional elements or ions. You will notice that A is the elemental reactant in each case. In the product, A ends up in the ionic compound. The element that A replaces depends on whether A is a metal or a non-metal. If A is a metal, then it replaces the cation. If A is a non-metal, then it replaces the anion. You need to ....

Analyze the two reactants in your equation and determine if the element is a metal or a non-metal. This will help you determine which element in the compound it will replace. Then determine the formula of the products. Take your time in doing this. And use some paper ... write some items down ... like the name of the elements that will be switching places and the names of the two products. Then use your formula writing skill to determine the formula of these two products. This may be the difficult part. Use the link below to assist with the determination of the formulae.

Writing Formualae for Ionic Compounds
 
One final caution, the element that stands alone as a product may be diatomic. You need to know that there are seven elements that exist in diatomic form when they are not combined with other elements in a compound or not present in an aqueous solution. Those seven elements are hydrogen (H), oxygen (O), nitrogen (N), chlorine (Cl), bromine (Br), idoine (I), and fluorine (F). To assist in recalling this list of 7 elements, you might remember the name HONClBrIF (pronounced "Honklebriff").
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