Chapter 4, Problem 4.70P

Interpretation Introduction

Interpretation:

The grams of ${\text{NaH}}_2{\text{PO}}_4$ needed to react with $43.74\text{ mL}$ of $0.285M\text{NaOH}$ is to be calculated.

Concept introduction:

Strong acids and strong bases are the substance that dissociates completely into its ions when dissolved in the solution. They dissociate completely in water to release ${\text{H}}^{+}$ ions and ${\text{OH}}^{-}$ ions.

Weak acids and weak bases are the substance that does not dissociate completely into its ions when dissolved in the solution. They dissociate partially in water to release ${\text{H}}^{+}$ ions and ${\text{OH}}^{-}$ ions.

Sodium dihydrogen phosphate $\left({\text{NaH}}_2{\text{PO}}_4\right)$ is a weak acid and sodium hydroxide $\left(\text{NaOH}\right)$ is a strong base. Sodium hydroxide $\left(\text{NaOH}\right)$ dissociates completely into ions and sodium dihydrogen phosphate $\left({\text{NaH}}_2{\text{PO}}_4\right)$ dissociates to some extent into ions. They both react to form sodium phosphate and a water molecule.

The molecular equation for the acid-base reaction of sodium dihydrogen phosphate and sodium hydroxide is:

${\text{NaH}}_2{\text{PO}}_4\left(s\right)+2\text{NaOH}\left(aq\right)\to {\text{Na}}_3{\text{PO}}_4\left(aq\right)+2{\text{H}}_2\text{O}\left(l\right)$