A) 771.4 kcal
B) 881.1 kcal
C) 871.2 kcal
D) 981.1 kcal
Correct Answer: A
Solution :
Given: Weight of benzoic acid = 1.89 g. Temperature of bomb calorimeter = \[25{}^\circ C\] = 298 K. Mass of water (m) = 18.94 kg = 18940 g. Increase in temperature (T) =\[0.632{}^\circ C\]. And specific heat of water (s) = 0.998 cal/g-deg. As we know that heat gained by water or heat liberated by benzoic acid (Q) = msT \[=18940\times 0.998\times 0.632=11946.14\text{ cal}\text{.}\] As 1.89 of acid liberates 11946.14 cal of heat, the heat liberated by 122 g of acid \[=\frac{11946.14\times 122}{1.89}\] \[=771126.5\,\text{cal=771}\text{.12}\,\text{kcal}\text{.}\] (Here 122 g is the molecular weight of benzoic acid) Hence, the correct option is (a).
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