Q. Which of the following mixing of 1 M base and 1 M acid leads to the largest increase in temperature?
A) 30 mL $CH_3COOH$ and 30 mL NaOH
B) 45 mL $CH_3COOH$ and 25 mL NaOH
C) 30 mL HCl and 30 mL NaOH
D) 50 mL HCl and 20 mL NaOH
Explanation
[Solution by Dr. Abubacker] Temperature rise $\propto\frac{\text{moles neutralised}\times|\Delta H|}{\text{total volume}}$. HCl + NaOH (strong-strong, $|\Delta H|\approx57$ kJ/mol) with $30$ mmol in $60$ mL gives the largest value. Option (1) has the same amounts but a weak acid (less heat released, part of it spent in ionisation); options (2) and (4) neutralise only $25$ and $20$ mmol in $70$ mL. Answer (3).
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.