Question

Phosphoric acid, which is commonly used as rust inhibitor, food additive and etching agent for dental and orthopedic use, can be synthesized using a two-step thermal process. In the first step, phosphorus and oxygen react to form diphosphorus pentoxide: P4(l)+5O2(g-2 P20s(g) In the second step, diphosphorus pentoxide and water react to form phosphoric acld P20(9)+3 H200 2H,PO40) Write the net chemical equation for the production of phosphoric acid from phosphorus, oxygen and water. Be sure your equation is balanced.

Answer 1

Answer: $P_4(l)+5O_2(g)+3H_2O(l)\rightarrow 2H_3PO_4(l)$  

Explanation:

We are given two reactions which are the two steps of a mechanism:

$P_4(l)+5O_2(g)\rightarrow 2P_2O_5(g)$       ......(1)

$P_2O_5(g)+3H_2O(l)\rightarrow 2H_3PO_4(l)$        .......(2)

To determine the net chemical equation, we will multiply equation 2

$P_2O_5(g)+3H_2O(l)\rightarrow 2H_3PO_4(l)\times 2$  

$2P_2O_5(g)+6H_2O(l)\rightarrow 4H_3PO_4(l)$ .......(3)

Adding (1) and (3)

$P_4(l)+5O_2(g)+3H_2O(l)\rightarrow 4H_3PO_4(l)$  

Thus, the net balanced chemical equation is:

$P_4(l)+5O_2(g)+3H_2O(l)\rightarrow 4H_3PO_4(l)$