Potassium peroxide is composed of 70.96% K and 29.04% O. Each peroxide ion has a net charge of 2-. (a) Given the molecular weight of the compound is 110.19, determine the chemical formula of potassium peroxide.

Verified step by step guidance

Step 1: Determine the molar mass of potassium (K) and oxygen (O) using the periodic table. Potassium has a molar mass of approximately 39.10 g/mol, and oxygen has a molar mass of approximately 16.00 g/mol.

Step 2: Assume you have 100 g of potassium peroxide. This means you have 70.96 g of K and 29.04 g of O. Convert these masses to moles by dividing by their respective molar masses: moles of K = 70.96 g / 39.10 g/mol and moles of O = 29.04 g / 16.00 g/mol.

Step 3: Calculate the mole ratio of K to O by dividing the moles of each element by the smallest number of moles calculated in Step 2. This will help determine the simplest whole number ratio of K to O in the compound.

Step 4: Use the information that each peroxide ion (O2^2-) has a net charge of 2- to deduce the number of oxygen atoms in the peroxide ion. This suggests that the peroxide ion consists of two oxygen atoms.

Step 5: Combine the information from the mole ratio and the charge of the peroxide ion to determine the empirical formula of potassium peroxide. Ensure the total molar mass of the empirical formula matches the given molecular weight of 110.19 g/mol.

Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Empirical Formula

The empirical formula represents the simplest whole-number ratio of elements in a compound. In the case of potassium peroxide, the percentages of potassium and oxygen can be converted into moles to find the ratio of K to O, which is essential for determining the empirical formula before deriving the molecular formula.

Molecular Weight

Molecular weight is the sum of the atomic weights of all atoms in a molecule, expressed in grams per mole. For potassium peroxide, knowing the molecular weight (110.19 g/mol) allows us to confirm the correct chemical formula by comparing it to the calculated weight based on the empirical formula.

Ionic Charge and Structure

Understanding ionic charges is crucial for determining the correct formula of ionic compounds. In potassium peroxide, the peroxide ion (O2^2-) has a net charge of 2-, which influences how potassium ions (K+) combine with peroxide to form the neutral compound, guiding the final chemical formula.

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Acetylene (C₂H₂) and nitrogen (N₂) both contain a triple bond, but they differ greatly in their chemical properties. (c) Write balanced chemical equations for the complete oxidation of N₂ to form N₂O₅(g) and of acetylene to form CO₂(g) and H₂O(g). Write a balanced chemical equation for the complete oxidation of acetylene to form CO₂(g) and H₂O(g).

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Textbook Question

Acetylene (C₂H₂) and nitrogen (N₂) both contain a triple bond, but they differ greatly in their chemical properties. (d) Calculate the enthalpy of oxidation per mole for N₂ and for C2H₂ (the enthalpy of formation of N₂O₅(g) is 11.30 kJ/mol).