Write the empirical formula of at least four binary ionic compounds that could be formed from the following ions:
[tex]$Zn^{2+}, Al^{3+}, F^{-}, O^{2-}$[/tex]
Answer (1)
Determine the charges of the given ions: Z n 2 + , A l 3 + , F − , O 2 − .
Combine Z n 2 + and F − to form Z n F 2 by balancing the charges.
Combine Z n 2 + and O 2 − to form Z n O by balancing the charges.
Combine A l 3 + and F − to form A l F 3 by balancing the charges.
Combine A l 3 + and O 2 − to form A l 2 O 3 by balancing the charges.
The four binary ionic compounds are: Z n F 2 , Z n O , A l F 3 , A l 2 O 3
Explanation
Understanding the Problem We are asked to determine the empirical formulas of at least four binary ionic compounds formed from the ions Z n 2 + , A l 3 + , F − , and O 2 − . A binary ionic compound consists of two elements, one a metal (cation) and the other a nonmetal (anion). The compound must be electrically neutral, meaning the total positive charge must equal the total negative charge.
Solution Strategy We will combine each cation with each anion to form a neutral compound. The empirical formula represents the simplest whole-number ratio of ions in the compound.
Zinc and Fluorine Compound
Zinc and Fluorine: Zinc has a +2 charge ( Z n 2 + ), and fluorine has a -1 charge ( F − ). To achieve neutrality, we need two fluoride ions for every zinc ion. Therefore, the empirical formula is Z n F 2 .
Zinc and Oxygen Compound
Zinc and Oxygen: Zinc has a +2 charge ( Z n 2 + ), and oxygen has a -2 charge ( O 2 − ). These charges balance in a 1:1 ratio. Therefore, the empirical formula is Z n O .
Aluminum and Fluorine Compound
Aluminum and Fluorine: Aluminum has a +3 charge ( A l 3 + ), and fluorine has a -1 charge ( F − ). To achieve neutrality, we need three fluoride ions for every aluminum ion. Therefore, the empirical formula is A l F 3 .
Aluminum and Oxygen Compound
Aluminum and Oxygen: Aluminum has a +3 charge ( A l 3 + ), and oxygen has a -2 charge ( O 2 − ). To achieve neutrality, we need to find the least common multiple of 2 and 3, which is 6. We need two aluminum ions (2 x +3 = +6) and three oxide ions (3 x -2 = -6). Therefore, the empirical formula is A l 2 O 3 .
Final Answer We have now determined the empirical formulas for four binary ionic compounds: Z n F 2 , Z n O , A l F 3 , and A l 2 O 3 .
Examples
Understanding how ionic compounds form is crucial in many real-world applications. For example, zinc oxide ( Z n O ) is used in sunscreen to block UV radiation, while aluminum oxide ( A l 2 O 3 ), also known as alumina, is used in abrasives and as a protective coating due to its hardness and inertness. The formation of these compounds relies on the principles of charge balance we've explored, ensuring stability and desired properties.
