Write the balanced chemical equation for the reaction of KHP with NaOH.
The correct answer and explanation is :
The reaction between potassium hydrogen phthalate (KHP) and sodium hydroxide (NaOH) is a typical acid-base reaction. KHP is an acidic compound, and NaOH is a strong base. The balanced chemical equation for this reaction is:
C₈H₅KO₄ (aq) + NaOH (aq) → C₈H₅NaO₄ (aq) + H₂O (l)
Explanation:
- KHP (Potassium Hydrogen Phthalate) is a weak acid that contains one acidic hydrogen atom. Its chemical formula is C₈H₅KO₄, and it consists of a phthalate group (C₈H₅O₄) with a potassium ion (K⁺) and a hydrogen atom (H⁺) attached. In solution, KHP dissociates into K⁺ and the phthalate anion (C₈H₅O₄⁻).
- NaOH (Sodium Hydroxide) is a strong base, meaning it dissociates completely in water into Na⁺ and OH⁻ ions.
In this reaction, the hydroxide ion (OH⁻) from NaOH reacts with the hydrogen ion (H⁺) from KHP, forming water (H₂O). The phthalate anion (C₈H₅O₄⁻) then combines with the sodium ion (Na⁺) from NaOH to form sodium phthalate (C₈H₅NaO₄).
- Balancing the equation: The equation is balanced in terms of atoms and charges. On the left side, KHP contributes a potassium ion (K⁺) and a phthalate ion (C₈H₅O₄⁻), and NaOH contributes sodium (Na⁺) and hydroxide (OH⁻). On the right side, the potassium ion (K⁺) and sodium ion (Na⁺) are associated with their respective counterions (phthalate and hydroxide), and water is formed from the reaction of H⁺ and OH⁻. Since each side contains 8 carbon atoms, 5 hydrogen atoms, 4 oxygen atoms, 1 sodium atom, and 1 potassium atom, the equation is balanced.
- Significance in titration: This reaction is often used in acid-base titrations, where KHP is used as a primary standard to determine the concentration of a sodium hydroxide solution. The balanced equation is essential for calculating the amount of NaOH required to neutralize a known quantity of KHP.