C6H5COOH 26.38 kJ/g 2.760 g 21.60℃ 29.93℃ 1.440 g 22.14℃ 27.09℃
Under constant-volume conditions,
the heat of combustion of benzoic acid (C6H5COOH) is 26.38 kJ/g.
A 2.760 g sample of benzoic acid is burned in a bomb calorimeter.
The temperature of the calorimeter increases from 21.60 to 29.93℃.
a) What is the total heat capacity of the calorimeter?
b) A 1.440 g sample of a new organic substance
is combusted in the same calorimeter.
The temperature of the calorimeter increases from 22.14 to 27.09℃.
What is the heat of combustion per gram of the new substance?
c) Suppose that in changing samples,
a portion of the water in the calorimeter were lost.
In what way, if any, would this change the heat capacity of the calorimeter?
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▶ 참고: 열용량과 비열
[ https://ywpop.tistory.com/2897 ]
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열용량, C = q / Δt
a)
(2.760 g) (26.38 kJ/g) / (29.93 – 21.60 ℃)
= (2.760) (26.38) / (29.93 – 21.60)
= 8.74055 kJ/℃
= 8.74 kJ/℃
b)
(8.74055 kJ/℃) (27.09 – 22.14 ℃) / (1.440 g)
= (8.74055) (27.09 – 22.14) / (1.440)
= 30.04564 kJ/g
= 30.0 kJ/g
c)
열량계에서 물이 손실되면
가열시킬 물의 양이 감소한 것이기 때문에,
동일한 양의 반응열(kJ)이 열량계에 가해지면
열량계의 온도는 더 크게 증가한다.
C = q / Δt 이므로,
즉, 열용량과 온도는 반비례하므로,
열량계의 열용량은 감소한다.
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