Apple wood is known to be one of the best firewoods available. It produces a hot

Question

Apple wood is known to be one of the best firewoods available. It produces a hot, aromatic fire and little ash. You are interested in determining the amount of heat available from a cord of apple wood. (Note, a cord is a measurement of volume equivalent to 128 ft3. A cord of apple wood weighs approximately 1900 kg.) You decide to measure its heat of combustion using a bomb calorimeter. You begin by standardizing the calorimeter using 1.124 grams of benzoic acid which has a heat of combustion of 6618 cal/gram. This combustion raised the temperature of the water bath by 2.321

Explanation / Answer

Calibration

Heat generated by burning benzoic acid= heat taken up by calorimeter+ water

let specific heat* mass of calorimeter be CP

so, by heat balance

1.124*6618=(CP+m*1)*2.321

or (CP+m)= 3204.925

now, in burning of applewood,

1.465*Heat of combustion= (CP+m)*1.643

so Heat of combustion= 3594.33 cal/gm

now, 1900*103 gm is 1 cord

so, 1 gm= 5.26*10-7 cord

so, heat of combustion= 3594.33/(5.26*10-7) cal/cord

= 6.83*109 cal/cord

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