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Question:

The true statement for the acids of phosphorus, H3PO2, H3PO3 and H3PO4 is:

all of them are tribasic acids

the order of their acidity is H3PO2 > H3PO3 > H3PO4

all of them are reducing in nature

the geometry of phosphorus is tetrahedral in all the three

Solution:

H3PO2, H3PO3 and H3PO4 are monobasic, dibasic and tribasic acids respectively. The order of their acidity increases as the number of O increases. The geometry of phosphorus is tetrahedral in all three. Phosphorous acid (H3PO3) is a reducing agent, while phosphoric acid (H3PO4) has less reducing property as the +5 oxidation state of phosphorus is more stable than +3.