To determine the oxidation state of chlorine in potassium chlorate (KClO₃), we need to analyze the compound step by step. ### Step 1: Understand the Composition of Potassium Chlorate Potassium chlorate is composed of three elements: potassium (K), chlorine (Cl), and oxygen (O). The chemical formula is KClO₃, which indicates that there is one potassium atom, one chlorine atom, and three oxygen atoms in each molecule of potassium chlorate. ### Step 2: Assign Known Oxidation States In order to find the oxidation state of chlorine, we can use the known oxidation states of the other elements in the compound: - **Potassium (K)**: This is an alkali metal and always has an oxidation state of +1 in its compounds. - **Oxygen (O)**: In most compounds, oxygen has an oxidation state of -2. ### Step 3: Set Up the Equation Now, we can set up an equation based on the overall charge of the compound. Potassium chlorate is a neutral compound, meaning the sum of the oxidation states must equal zero. Let’s denote the oxidation state of chlorine as \( x \). The equation based on the oxidation states will be: \[ \text{Oxidation state of K} + \text{Oxidation state of Cl} + 3 \times \text{Oxidation state of O} = 0 \] Substituting the known values: \[ (+1) + x + 3(-2) = 0 \] ### Step 4: Solve the Equation Now, we can simplify and solve for \( x \): \[ 1 + x - 6 = 0 \] \[ x - 5 = 0 \] \[ x = +5 \] ### Conclusion The oxidation state of chlorine in potassium chlorate (KClO₃) is +5. Therefore, the correct answer is **D. +5**. ### Explanation of Other Options - **A. +1**: This is incorrect because if chlorine had an oxidation state of +1, the equation would not balance. The contribution from oxygen would not allow for a neutral compound. - **B. +2**: This is also incorrect for the same reason as option A. The oxidation states would not sum to zero when considering the contributions from potassium and oxygen. - **C. +3**: While this is a possible oxidation state for chlorine in some compounds, it does not apply here. The calculations show that the oxidation state must be +5 to achieve a neutral compound. ### Common Pitfalls - **Misunderstanding Oxidation States**: Students often confuse oxidation states with the actual charge of the ion. Remember, oxidation states are hypothetical charges based on electron distribution. - **Ignoring the Neutrality of Compounds**: Always remember that the sum of oxidation states in a neutral compound must equal zero. - **Overlooking the Contribution of Multiple Atoms**: When multiple atoms of an element are present (like the three oxygen atoms in KClO₃), ensure to multiply their oxidation state by the number of atoms. ### Revision Summary - The oxidation state of chlorine in potassium chlorate (KClO₃) is +5. - Potassium has an oxidation state of +1, and oxygen typically has an oxidation state of -2. - The sum of oxidation states in a neutral compound must equal zero. - Always carefully set up equations based on known oxidation states to find unknowns.