Write the balanced molecular equation between phosphoric acid (H:PO4) and sodium hydroxide (NaOH).
The Correct Answer and Explanation is :
The balanced molecular equation for the reaction between phosphoric acid (H₃PO₄) and sodium hydroxide (NaOH) is:
H₃PO₄ (aq) + 3 NaOH (aq) → Na₃PO₄ (aq) + 3 H₂O (l)
Explanation:
Phosphoric acid (H₃PO₄) is a triprotic acid, meaning it can donate three hydrogen ions (H⁺) in a reaction. Sodium hydroxide (NaOH) is a strong base that dissociates completely in water to produce hydroxide ions (OH⁻). In the reaction, the hydroxide ions from NaOH neutralize the hydrogen ions from H₃PO₄, resulting in the formation of water and a salt. The specific steps of the reaction are as follows:
- Step 1: Ionization of Phosphoric Acid
Phosphoric acid dissociates in water into hydrogen ions (H⁺) and the phosphate ion (H₂PO₄⁻), though it can release up to three protons in total. The initial dissociation is:
[
H₃PO₄ \rightleftharpoons H⁺ + H₂PO₄⁻
] - Step 2: Neutralization with Sodium Hydroxide
Sodium hydroxide dissociates in water into sodium ions (Na⁺) and hydroxide ions (OH⁻). Each OH⁻ ion can neutralize one H⁺ ion. As phosphoric acid has three replaceable hydrogen ions, three OH⁻ ions will be required to fully neutralize the acid. - Step 3: Formation of Water and Salt
Each hydrogen ion (H⁺) reacts with a hydroxide ion (OH⁻) to form water (H₂O). The phosphate ion (PO₄³⁻) will combine with sodium ions (Na⁺) to form sodium phosphate (Na₃PO₄), the salt produced in the reaction. - Step 4: Balanced Equation
Since three hydroxide ions are required to neutralize all three hydrogen ions from phosphoric acid, the balanced equation is:
[
H₃PO₄ + 3 NaOH → Na₃PO₄ + 3 H₂O
]
This reaction is a typical example of an acid-base neutralization, where an acid (phosphoric acid) reacts with a base (sodium hydroxide) to produce a salt (sodium phosphate) and water.