1. Tardigrade
  2. Question
  3. Chemistry
  4. When 400 mL of 0.2 N solution of a weak acid is neutralised by a dilute aqueous solution of sodium hydroxide under standard conditions, 4.4 kJ amount of heat is liberated. Therefore, the standard enthalpy bf neutralisation of this weak acid, in k J equiv -1, is

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Q. When $400 \,mL$ of $0.2 \,N$ solution of a weak acid is neutralised by a dilute aqueous solution of sodium hydroxide under standard conditions, $4.4 \,kJ$ amount of heat is liberated. Therefore, the standard enthalpy bf neutralisation of this weak acid, in $k J$ equiv $^{-1}$, is

J & K CETJ & K CET 2009Thermodynamics

Solution:

Heat of neutralisation is the heat that evolved when one equivalent of acid is neutralised by one equivalent of a base.
$\because$ Milliequivalents of weak acid $=400 \times 0.2$
$=80$ milliequivalents $\therefore $ Equivalents of the acid $=0.08$ equivalent.
Since, heat evolved when $0.08$ equivalent of acid is neutralised
$=4.4 \,kJ$
$\therefore $ The heat evolved, when $1$ equivalent is neutralised
$=\frac{4.4 \times 1}{0.08}=55 \,k J$ equiv $^{-1}$.