Question

Which is not appropriate method of making orthophosphoric acid?

• A. $P_4{O}_{10}+6H_{2}O\to 4H_{3}P{O}_4$
• B. $P{H}_3+2O_2\to H_{3}P{O}_4$
• C. $P_4+16H_{2}O\to 4H_{3}P{O}_4+2H_2$
• D. $PC{l}_5+4H_{2}O\to H_{3}P{O}_4+5HCl$

Answer 1

The correct option is A $P_4{O}_{10}+6H_{2}O\to 4H_{3}P{O}_4$

Phosphoric acid is a weak acid which is used in making fertilizers and in laundry. It is a colorless odourless crystalline liquid.

While all the other reactions can easily give $H_{3}P{O}_4$ acid, the reaction (A) does not. When $P_4{O}_{10}$ reacts with water, the reaction becomes highly exothermic and forms fumes of $H_{3}P{O}_4$.