Which of the following best represents a double replacement reaction?
A. A + B --> A + B
B. A + B --> AB
C. A + BC --> AC + B
D. AC + BD --> AD + BC
Answer (2)
Double replacement reactions involve the exchange of ions between two reactants.
The general form of a double replacement reaction is A X + B Y → A Y + BX .
Analyze each option to see which one fits the general form.
The correct answer is A C + B D → A D + BC .
Explanation
Understanding Double Replacement Reactions We want to identify the reaction that represents a double replacement. In a double replacement reaction, two compounds react, and the positive ions (cations) and the negative ions (anions) of the two reactants switch places, forming two new compounds. The general form is: A X + B Y → A Y + BX
Analyzing Each Option Let's examine each option:
Option 1: AB -> A + B
This represents a decomposition reaction, where a single compound breaks down into simpler substances.
Option 2: A + B -> AB
This represents a combination or synthesis reaction, where two or more substances combine to form a single compound.
Option 3: A + BC -> AC + B
This represents a single replacement reaction, where one element replaces another in a compound.
Option 4: AC + BD -> AD + BC
This fits the general form of a double replacement reaction. The cations switch anions.
Identifying the Correct Reaction The equation that best represents a double replacement reaction is: A C + B D → A D + BC
Examples
Double replacement reactions are commonly used in water treatment to remove unwanted ions. For example, adding calcium hydroxide (lime) to hard water containing calcium bicarbonate will cause a double replacement reaction, precipitating calcium carbonate, which can then be filtered out, softening the water. This process is crucial for both industrial and domestic water supplies, ensuring water is safe and suitable for various uses.
The best representation of a double replacement reaction is A C + B D → A D + BC . This type of reaction involves the exchange of ions between two compounds to form two new compounds. The other options do not fit the criteria for double replacement reactions.
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