Question

An aqueous solution containing 7.22 g NaOH is added to an aqueous solution containing 18.4 g H3PO4.

(a) Write a balanced equation for the acid-base reaction that should occur. (Include physical states.)

(b) Identify the limiting reactant.

NaOH or H₃PO₄

(c) Will the solution be acidic or basic when the reaction is complete?

Answer 1

a. Equation of the reaction: 3 NaOH_(aq) + H₃PO_4(aq) Na₃PO_4(aq) + 3 H₂O_(l)

b. Moles of NaOH = mass / molar mass = 7.22 / 40 = 0.180 mol

Moles of H₃PO₄ = mass / molar mass = 18.4 / 98 = 0.188 mol

Since each mole of H₃PO₄ needs 3 moles of NaOH butthe reaction has almost equal moles of both, NaOH is the limiting reagent

c. Since there is acid leftover, the solution will be acidic