Question

How many grams of phosphoric acid is required to completely neutralise 120g of sodium hydroxide?

• A. 49
• B. 98
• C. 196
• D. 9.8

Answer 1

Answer: (B)

Equation of orthophosphoric acid with sodium hydroxide is given as : $\underset{\begin{array}{c}\text{1}\text{mole}\\ \text{= 3}\text{+}\text{31}\text{+}\text{64}\\ \text{=}\text{98}\text{g}\end{array}}{H_{3}P{O}_4}+\underset{\begin{array}{rl}& \text{3}\text{mole}\\ & \text{3}\times (23+16+1)\\ & =3\times 40\\ & =120g\end{array}}{3NaOH}\to N{a}_{3}P{O}_4+3H_{2}O$ It is clear from the above equation that 120 g of NaOH is neutralised by 98 g of ${\text{H}}_{\text{3}}\text{P}{\text{O}}_{\text{4}}\text{.}$