1.

When 100 mL of 1.0 M HCl was mixed 100 mL of 1.0 M NaOH in an insulated beaker at constant pressure, a temperature increase `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 kJmol^(-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 `(K_(a)=2.0xx10^(-5))` was mixed with 100 mL of 1.0 M NaOH (under indentical conditions to Expt. 1) where a temperature rise of `5.6^(@)C` was measured (Consider heat capacity of all solutions as `4.2 Jg^(-1)K^(-1)` and density of al solutions as 1.0 gm`L^(-1)`) The pH of the solution after Expt. 2 isA. `2.8`B. `4.7`C. `5.0`D. `7.0`

Answer» Correct Answer - B
Final solution contain 0.1 mole of `CH_(3)COOH` and `CH_(3)COONa` each
Hence it is buffer solution
`pH=pK_(a)+log.([CH_(3)COO^(-)])/([CH_(3)COOH])=5-log2+log.(0.1)/(0.1)=4.7`


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