# Determining Oxidation Numbers of KClO3, NH4+, Cr2O72-, MnO42-

• ipl
In summary, the conversation is about determining the oxidation numbers of different elements in chemical formulas. The speaker asks for an explanation of the oxidation numbers in KClO3, NH4+, Cr2O72-, and MnO42-. The responder explains that there are simple rules to follow and provides an example for KClO3, stating that Cl is +5. When asked for an explanation, the responder suggests following the rules and calculating the oxidation numbers based on the charges of the atoms in the molecule. The conversation ends with the mention of methods and rules for determining oxidation numbers.
ipl
Determine the oxidation numbers of the underlined elements in the following formulas:?
If you could explain each one, it would be greatly appreciated. Thanks!
a) KClO3
b) NH4+
c) Cr2O72-
d) MnO42-

Okay is a) +5 because K=+1 and O=-2? I'm just wondering cause someone posted that on yahoo.

Yep, Cl in KClO3 is +5 (regardless of what was posted on Yahoo).

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do you think you could explain to me why?

Because it can be calculated following rules from the page I have linked to?

Nothing magic about it. Molecule is neutral, K is +1 (one of the rules), O is -2 (one of the rules), so Cl+1+3*(-2)=0.

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methods

## 1. What is the oxidation number of potassium (K) in KClO3?

The oxidation number of potassium in KClO3 is +1. This is because the overall charge of the compound is 0, and the oxidation number of oxygen is usually -2. Therefore, the oxidation number of potassium can be calculated by setting up the equation: x + (-2) + (-2) + (-2) = 0. Solving for x gives a value of +1.

## 2. What is the oxidation number of nitrogen (N) in NH4+?

The oxidation number of nitrogen in NH4+ is -3. This is because the overall charge of the compound is +1, and the oxidation number of hydrogen is usually +1. Therefore, the oxidation number of nitrogen can be calculated by setting up the equation: (-3) + 4(+1) = +1. Solving for x gives a value of -3.

## 3. What is the oxidation number of chromium (Cr) in Cr2O72-?

The oxidation number of chromium in Cr2O72- is +6. This is because the overall charge of the compound is -2, and the oxidation number of oxygen is usually -2. Therefore, the oxidation number of chromium can be calculated by setting up the equation: 2x + 7(-2) = -2. Solving for x gives a value of +6.

## 4. What is the oxidation number of manganese (Mn) in MnO42-?

The oxidation number of manganese in MnO42- is +7. This is because the overall charge of the compound is -2, and the oxidation number of oxygen is usually -2. Therefore, the oxidation number of manganese can be calculated by setting up the equation: x + 4(-2) = -2. Solving for x gives a value of +7.

## 5. How do you determine the oxidation numbers of a compound?

To determine the oxidation numbers of a compound, you can follow a few steps. First, identify the elements in the compound and their known oxidation numbers. Then, set up an equation using the overall charge of the compound and the known oxidation numbers. Finally, solve for the unknown oxidation numbers by balancing the equation. Keep in mind that some elements, like hydrogen and oxygen, have common oxidation numbers that can be used as a guide. Additionally, the sum of all oxidation numbers in a neutral compound should equal 0, while in an ion, it should equal the overall charge of the ion.

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