What is the oxidation number of As in K3AsO4

What is the oxidation number of As in K3AsO4
what is the oxidation number of As in K3AsO4

The Correct Answer and Explanation is:

Oxidation Number of As in K₃AsO₄:

The oxidation number of arsenic (As) in potassium arsenate (K₃AsO₄) is +5.

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Step-by-Step Determination:

To determine the oxidation number of As in K₃AsO₄, follow these steps:

1. Assign oxidation numbers to known elements:
   • Potassium (K) is an alkali metal and always has an oxidation number of +1.
   • Oxygen (O) almost always has an oxidation number of –2.
2. Set up an equation using the chemical formula:
   • There are 3 potassium atoms, each with +1 charge → total +3.
   • There are 4 oxygen atoms, each with –2 charge → total –8.
   • Let the oxidation number of arsenic (As) be x.
   The compound is neutral overall, so the sum of the oxidation numbers must be zero: 3(+1)+x+4(–2)=03+x–8=0x–5=0x=+53(+1) + x + 4(–2) = 0 \\ 3 + x – 8 = 0 \\ x – 5 = 0 \\ x = +5

Therefore, the oxidation number of As is +5.

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Explanation

Understanding oxidation numbers is essential in redox chemistry, as it helps identify which atoms are oxidized or reduced in a reaction. In K₃AsO₄ (potassium arsenate), potassium is an alkali metal that consistently carries a +1 oxidation state. Each potassium atom donates one electron, leading to a total contribution of +3 from the three potassium atoms.

Oxygen is typically assigned an oxidation number of –2, especially when it’s bonded in compounds like oxides or oxyanions. In K₃AsO₄, there are four oxygen atoms contributing a total of –8.

Since K₃AsO₄ is a neutral compound, the sum of all oxidation numbers must equal zero. This principle is fundamental in chemistry — the total charge of the compound must match the sum of the oxidation states of all atoms involved.

By assigning +1 to each K and –2 to each O, and solving for the unknown oxidation number of As, we find that As must be +5 to balance the total charge. This means arsenic is in its highest common oxidation state in this compound.

In summary, the oxidation number of arsenic in K₃AsO₄ is +5, determined through standard rules of assigning oxidation numbers and ensuring the compound’s total charge remains neutral. This information is vital in understanding the behavior of arsenic in chemical reactions, especially in redox and coordination chemistry.