Ionic equilibrium
Question

# When 100 mL of 1.0 M HCl was mixed with 100 mL of 1.0 M NaOH in an insulated beaker at constant pressure, a temperature increase of 5.7°C was measured for the beaker and its contents (Expt. 1). Because the enthalpy of neutralization of a strong acid with a strong base is a constant (-57.0 kJ mol-1), this experiment could be used to measure the calorimeter constant. In a second experiment (Expt. 2), 100 mL of 2.0 M acetic acid (Ka = 2.0 × 10-5) was mixed with 100 mL of 1.0 M NaOH (under identical conditions to Expt. 1) where a temperature rise of 5.6°C was measured.(Consider heat capacity of all solutions as 4.2 J g-1K-1 and density of all solutions as 1.0 g mL-1)

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Solution

## For Expt (1) Q = msx(+57) For neutralization of 100m kg of strong acid with strong base          For 1 gr equivalent of strong acid (vs) strong base; Enthalpy of neutralization is – 57 kg          \ Calometric constant =$1kJ.{k}^{-1}$          For expt (2)          100 ml of 2m acetic acid (vs) 100ml of 1 M NaOH is the neutralization 100 meq acetic acid is neturalisation with (or) meq of NaOH          Q = msX (+5.6) = 1×5.6 kJ / 100 ml          For 1000 meq ® 56 kJ          \ Q = Enthalpy of dissociation of acetic acid = 1 kJ

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