predicting+products

In order to predict the products of a chemical reaction, you must first be able to identify the type of reaction that will occur.

Here are two basic reaction types to start with:
 * single replacement: A + BC --> AC + B
 * double replacement: AB + CD --> AD + CB

The letter patterns shown above should be used in predicting the arrangement of atoms in the products of a reaction.


 * Predicting products of a single replacement reaction: A + BC --> AC + B**

__Example:__ Predict the products of the reaction when copper metal is immersed in a solution of zinc chloride.

Solution:

Single replacement reactions always involve a lone element - in this case, copper. This is "A" in the reaction A + BC.

The "BC" is a compound, zinc chloride. Zinc is "B" and chloride is "C".

The reactants side of the equation is therefore:


 * Cu (s) + || Zn || Cl 2 (aq) || --> ||
 * A || B || C ||  ||

To predict the products, use the letter pattern AC + B. This would be copper chloride (AC) and zinc (B). Now complete the equation:


 * Cu (s) + || Zn || Cl 2 (aq) || --> || Cu || Cl 2 + || Zn ||
 * A || B || C ||  || A || C || B ||

The phases of the products can be predicted using the periodic table and the solubility rules. Zinc is a metal, and copper chloride is aqueous due to the chloride ion.

Final answer:


 * Cu (s) + || Zn || Cl 2 (aq) || --> || Cu || Cl 2 (aq) + || Zn (s) ||


 * Predicting products of a double replacement reaction: AB + CD --> AD + CB**

__Example:__

Predict the products of a reaction between aqueous solutions of calcium chloride and potassium carbonate.

Solution:

Apply the letter pattern "AB" to calcium chloride, and "CD" to potassium carbonate.

A = calcium B = chloride C = potassium D = carbonate

Then use the product patterns "AD" and "CB" to form the products:

AD = calcium carbonate CB = potassium chloride

Therefore:

calcium chloride + potassium carbonate --> calcium carbonate + potassium chloride

Next, determine the chemical formulas:

CaCl 2 + K 2 CO 3 --> CaCO 3 + KCl

Here is the chemical equation with letters:


 * Ca || Cl 2 + || K 2 || CO 3 || --> || Ca || CO 3 + || K || Cl ||
 * A || B || C || D ||  || A || D || C || B ||

Next, balance the chemical equation.

CaCl 2 + K 2 CO 3 --> CaCO 3 + __2__ KCl

Finally, predict the solubilities of each substance. Hint: the reactants were both solutions (aqueous).

CaCl 2 (aq) + K 2 CO 3 (aq) --> CaCO 3 (s) + 2 KCl (aq)

Practice worksheets: