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Ch.7 - Periodic Properties of the Elements
Chapter 7, Problem 66

Write balanced equations for the following reactions: (a) sulfur dioxide with water (b) lithium oxide in water (c) zinc oxide with dilute hydrochloric acid (d) arsenic trioxide with aqueous potassium hydroxide.

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Identify the reactants: Arsenic trioxide (As2O3) and potassium hydroxide (KOH).
Determine the products: When arsenic trioxide reacts with a strong base like potassium hydroxide, it forms potassium arsenite (K3AsO3) and water (H2O).
Write the unbalanced chemical equation: As2O3 + KOH ightarrow K3AsO3 + H2O.
Balance the equation by adjusting the coefficients to ensure the number of atoms for each element is equal on both sides of the equation. Start by balancing the arsenic (As) and oxygen (O) atoms, then adjust the potassium (K) and hydrogen (H) atoms.
Check the final balanced equation to ensure mass and charge are balanced.

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Key Concepts

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

Balancing Chemical Equations

Balancing chemical equations involves ensuring that the number of atoms for each element is the same on both the reactant and product sides. This is based on the law of conservation of mass, which states that matter cannot be created or destroyed in a chemical reaction. To balance an equation, coefficients are adjusted in front of the chemical formulas, rather than changing the formulas themselves.
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Acid-Base Reactions

Acid-base reactions typically involve the transfer of protons (H⁺ ions) between reactants. In this case, arsenic trioxide (As₂O₃) can react with potassium hydroxide (KOH), which is a strong base, to form a salt and water. Understanding the nature of the reactants and the products formed is crucial for predicting the outcome of the reaction.
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Solubility and Aqueous Solutions

In aqueous solutions, the solubility of compounds plays a significant role in determining the products of a reaction. Potassium hydroxide is soluble in water, dissociating into K⁺ and OH⁻ ions. Knowing the solubility of arsenic compounds helps predict whether a precipitate will form or if the reaction will proceed in solution, which is essential for writing the balanced equation.
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