Explain Why Hypophophorous Acid Acts As Reducing Agent But Phosphoric Acid Does Not?

H3PO4, phosphorous acid, is the most stable form of a __phosphor___ acid

In H3PO4 H3 = +3, P = __ O4 = -8

In H3PO4 the charge on P = +5

The 4 O atoms have attracted 5 electrons from the P atom.

These were the 3s2, 3p3 electrons, leaving the P atom with 2s2, sp8, an octet, a stable state.

Hypophosphoric acid = H3PO2

In H3PO2, H3 =+3, P = ___, O2 = -4

In H3PO2, the charge on P = +1

One of the O atoms has attracted 1 electron from the P atom.

This electron came from were the 3s2, 3p3 electrons, leaving the P atom with 3s2, 3p2 an unstable state.

The P atom in H3PO2 needs to lose the 4 electrons, 3s2, 3p2, to be stable. This means the H3PO2 is oxidized, as it reduces a nonmetal such as I2.

Phosphoric acid removes the zinc coating from roofing nails. It is an ingredient in Toilet bowl cleaner.

The reaction equation is ;

Zn + H3PO4 à + Zn3(PO4)2 + H2

Zn = 0 charge is oxidized to Zn +2 charge in the Zn3(PO4)2; as H+1 charge in the H3(PO4)3 is reduced to H = 0 charge in H2. The H2 is the oxidizing agent, and the Zn is the reducing agent.

The H in the Phosphoric acid causes Zinc to be oxidized from Zn = 0 charge to Zn = +2 charge. Thus Phosphoric acid provides an oxidizing agent.