Question

Sodium pyrophosphate is represented by which of the following formula?

• A. $Na_2P_2O_4$
• B. $Na_4P_2O_5$
• C. $Na_4P_2O_7$
• D. $Na_2P_2O_5$

Answer 1

Answer: (C)

$Na_4P_2O_7$

Answer 2

Sodium pyrophosphate is represented by $Na _{4} P _{2} O _{7} .$ It is sodium salt of pyrophosphoric acid $\left( H _{4} P _{2} O _{7}\right)$, which may be considered to be made up by two molecules of ortho phosphoric acid $\left( H _{3} PO _{4}\right)$, eleminating one molecule of $H _{2} O$. $2H_3PO_4 {->[-H_2O]} \underset{\text{Pyrophosphoric acid}}{H_4P_2O_7}$