Question

Assign oxidation number to each atom in the following species a.Cr(OH)4-

Answer 1

Answer : The oxidation number of chromium (Cr) is, (+3)

Explanation :

Oxidation number : It represent the number of electrons lost or gained by the atoms of an element in a compound.

Oxidation numbers are generally written with the sign (+) and (-) first and then the magnitude.

When the atoms are present in their elemental state then the oxidation number will be zero.

Rules for Oxidation Numbers :

• The oxidation number of a free element is always zero.
• The oxidation number of a monatomic ion equals the charge of the ion.
• The oxidation number of  Hydrogen (H)  is +1, but it is -1 in when combined with less electronegative elements.
• The oxidation number of  oxygen (O)  in compounds is usually -2, but it is -1 in peroxides.
• The oxidation number of a Group 1 element in a compound is +1.
• The oxidation number of a Group 2 element in a compound is +2.
• The oxidation number of a Group 17 element in a binary compound is -1.
• The sum of the oxidation numbers of all of the atoms in a neutral compound is zero.
• The sum of the oxidation numbers in a polyatomic ion is equal to the charge of the ion.

The given compound is, $Cr(OH)_4^-$

Let the oxidation state of 'Cr' be, 'x'

$x+4(-2+1)=-1\\\\x+4(-1)=-1\\\\x-4=-1\\\\x=+3$

Therefore, the oxidation number of chromium (Cr) is, (+3)

Answer 2

Answer:

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