Question

Given,\[{H_3}P{O_4}\] is a tribasic acid and one of its salts is \[Na{H_2}P{O_4}\]. What volume in ml of \[1M\]$NaOH$ solution should be added to \[12g\]of \[Na{H_2}P{O_4}\] to convert it into \[N{a_3}P{O_4}\]?

Answer 1

Hint: We have to know that the trisodium phosphate is an inorganic compound having the chemical formula, \[N{a_3}P{O_4}\] which is a white crystalline solid and it is completely soluble in water. The phosphoric acid is a tribasic acid having the formula, \[{H_3}P{O_4}\]. The pure phosphoric acid is a colorless liquid. The monosodium phosphate is otherwise known as monobasic sodium phosphate which is an inorganic compound having the formula, \[Na{H_2}P{O_4}\].

Complete answer:
The phosphoric acid is a tribasic acid. Because it can replace three hydrogen atoms. The reaction of formation of \[N{a_3}P{O_4}\] is written as,
\[Na{H_2}P{O_4} + 2NaOH \to N{a_3}P{O_4} + {H_2}O\]
Here we can say that one mole of \[Na{H_2}P{O_4}\] needs two moles of sodium hydroxide.
The molar mass of \[Na{H_2}P{O_4}\] is equal to \[120g/mol\]. Hence, the number of moles of \[Na{H_2}P{O_4}\]for \[12g\] is equal to \[0.1mol\].
Thus,
The number of moles of sodium hydroxide consume for the reaction\[ = 2 \times 0.1mol = 0.2mol\]
The molarity of sodium hydroxide is equal to \[1mol/L\]. Therefore, the volume of one mole of sodium hydroxide is equal to \[1L\].
So, volume of \[0.2molNaOH = 1 \times 0.2L\]
$ = 0.2L$
Now we converting liter into milliliter we get,
$ = 0.2 \times 1000ml$
$ = 200ml$
Hence, \[200mL\] of one mol of $NaOH$ is to be added to\[12g\] of \[Na{H_2}P{O_4}\] to convert \[N{a_3}P{O_4}\].

Note:
We have to know that the phosphoric acid can replace three hydrogen atoms, hence it is a tribasic acid. The phosphoric acid is also known as orthophosphoric acid which acts as an oxidizing agent. This is the main difference of the orthophosphoric acid from other phosphoric acid. And the oxidation state of phosphoric acid is \[ + 5\]. This phosphoric acid soluble in both water and the alcohol and it is used to make fertilizers.