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Standard XII

Chemistry

Heat of Reaction

A constant pr...

Question

A constant pressure calorimeter consists of an insulated beaker of mass $82 g$ made up of glass with heat capacity $0.75 J K^{- 1} g^{- 1}$ . The beaker contains $100 m L$ of $1 M$ $H C l$ at ${22.6}^{o} C$ to which $100 m L$ of $1 M$ $N a O H$ at ${23.4}^{o} C$ is added. The final temperature after the reaction is complete at ${29.3}^{o} C$ . What is $Δ H$ per mole for this neutralisation reaction? Assume tha the heat capacities of all solutions are equal to that of same volumes of water.

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Solution

Initial average temperature of the acid and base
$= \frac{22.6 + 23.4}{2} = {23.0}^{o} C$
Rise in temperature $= (29.3 - 23.0) = {6.3}^{o} C$
Total heat produced $= (92 \times 0.75 + 200 \times 4.184) \times 6.3 = 5706.54 J$
Enthalpy of neutralization $= - \frac{5706.54}{100} \times 1000 \times 1 = - 57 k J$

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Initial average temperature of the acid and base=22.6+23.42=23.0oCRise in temperature=(29.3−23.0)=6.3oCTotal heat produced=(92×0.75+200×4.184)×6.3=5706.54JEnthalpy of neutralization =−5706.54100×1000×1=−57kJ