Heat capacity of a bomb calorimeter

Finally, we note that the heat capacity of a bomb calorimeter is usually determined by burning in it a compound with an accurately known heat of combustion value. From the mass of the compound and the temperature increase, we can calculate the heat capacity of the calorimeter (see Problem 6.94). 

The heat capacity of a bomb calorimeter was determined by burning 6.79 g of methane (energy of combustion = 802 kJ/mol... 

The heat capacity of a bomb calorimeter must be determined by experiment. 

PRACTICE EXAMPLE B The heat of combustion of benzoic acid, CgH5CCX3H(s), is —26.42 kj/g. One method of obtaining the heat capacity of a bomb calorimeter is to measure the temperature change produced by the combustion of a given mass of benzoic acid. If the combustion of a 1.176 g sample of benzoic acid causes a temperature increase of 4.96 °C in a bomb calorimeter assembly, what is the heat capacity of the assembly ... 

Salicylic acid, C7H6O3, has been suggested as a calorimetric standard. Its heat of combustion is -3.023 X 10 kJ/molC7H603. From the following data determine the heat capacity of a bomb calorimeter assembly (that is, the bomb, water, stirrer, thermometer, wires, and so forth). 

Isooctane is a primary component of gasoline and gives gasoline its octane rating. Burning 1.00 mL of isooctane (d = 0.688 g/mL) releases 33.0 kj ofheat. When 10.00 mL of isooctane is burned in a bomb calorimeter, the temperature in the bomb rises from 232°C to 66.5°C. What is the heat capacity of the bomb calorimeter ... 

A quantity of 1.435 g of naphthalene (CioHg), a pungent-smeUing substance used in moth repellents, was burned in a constant-volume bomb calorimeter. Consequently, the temperature of the water rose from 20.17°C to 25.84°C. If the mass of water surrounding the calorimeter was exactly 2000 g and the heat capacity of the bomb calorimeter was 1.80 kJ/°C, calculate the heat of combustion of naphthalene on a molar basis that is, find the molar heat of combustion. 

FOLLOW-UP PROBLEM 6.5 A chemist burns 0.8650 g of graphite (a form of carbon) in a new bomb calorimeter, and CO2 forms. If 393.5 kJ of heat is released per mole of graphite and T increases 2.613 K, what is the heat capacity of the bomb calorimeter ... 

When 1.010 g of sucrose (C12H22O11) undergoes combustion in a bomb calorimeter, the temperature rises from 24.92 °C to 28.33 °C. Find for the combustion of sucrose in kJ/mol suCTose. The heat capacity of the bomb calorimeter, determined in a separate experiment, is 4.90 kJ/"C. (You can ignore the heat capacity of the small sample of sucrose because it is negligible compared to the heat capacity of the calorimeter.)... 

A 1.620 g sample of naphthalene, CioHg(s), is completely burned in a bomb calorimeter assembly and a temperature increase of 8.44 °C is noted. If the heat of combustion of naphthalene is -5156 kj/mol CioHg, what is the heat capacity of the bomb calorimeter ... 

A 1.397 g sample of thymol, C4oHi40(s) (a preservative and a mold and mildew preventative), is burned in a bomb calorimeter assembly. The temperature increase is 11.23 C,and the heat capacity of the bomb calorimeter is 4.68 kJ/"C. What is the heat of combustion of thymol, expressed in kilojoules per mole of C10H14O ... 

The heat capacity of a gas at constant pressure is nonually detenuined in a flow calorimeter. The temperature rise is detenuined for a known power supplied to a gas flowing at a known rate. For gases at pressures greater than about 5 MPa Magee et al [13] have recently described a twin-bomb adiabatic calorimeter to measure Cy. 

A chemist wants to calibrate a new bomb calorimeter. He completely burns a mass of 0.930 g of carbon in a calorimeter. The temperature of the calorimeter changes from 25.00°C to 28.15°C. If the thermal energy change is 32.8 kj/g of carbon burned, what is the heat capacity of the new calorimeter What evidence shows that the reaction was exothermic ... 

The combustion of 0.1584 g of benzoic acid increases the temperature of a bomb calorimeter by 2.54°C. Calculate the heat capacity of the calorimeter. (The energy released by combustion of benzoic acid is 26.42 kj/g.) A 0.2130-g sample of vanillin (C8HgC>3) is then burned in the same calorimeter. The temperature increases by 3.25°C. What is the energy of combustion per gram of vanillin and per mole of vanillin ... 

A nutritionist determines the caloric value of a 10.00-gram sample of beef fat by burning it in a bomb calorimeter. The calorimeter held 2.500 kg of water, the heat capacity of the bomb is 1.360 kJ/°C, and the temperature of the calorimeter increased from 25.0°C to 56.9°C. (a) Calculate the number of joules released per gram of beef fat. (b) One nutritional Calorie is 1 kcal or 4184 joules. What is the dietary, caloric value of beef fat, in nutritional Calories per gram ... 

Constant-Volume Calorimetry In the coffee-cup calorimeter, we assume all the heat is gained by the water, but some must be gained by the stirrer, thermometer, and so forth. For more precise work, as in constant-volume calorimetry, the heat capacity of the entire calorimeter must be known. One type of constant-volume apparatus is the bomb calorimeter, designed to measure very precisely the heat released in a combustion reaction. As Sample Problem 6.5 will show, this need for greater precision requires that we know (or determine) the heat capacity of the calorimeter. 

Figure 6.8 (on the next page) depicts the preweighed combustible sample in a metal-walled chamber (the bomb), which is filled with oxygen gas and immersed in an insulated water bath fitted with motorized stiirer and thermometer. A heating coil connected to an electrical source ignites the sample, and the heat evolved raises the temperature of the bomb, water, and other calorimeter parts. Because we know the mass of the sample and the heat capacity of the entire calorimeter, we can use the measured AT to calculate the heat released. 

The enthalpy of combustion of benzoic acid (CgHsCOOH) is commonly used as the standard for calibrating constant-volume bomb calorimeters its value has been accurately determined to be —3226.7 kJ/mol. When 1.9862 g of benzoic acid are burned in a calorimeter, the tempo ature rises from 21.84°C to 25.67°C. What is the heat capacity of the bomb (Assume that the quantity of water surrounding the bomb is exactly 2000 g.)... 

The representation of the calorimeter by mathematical models described by a set of heat balance equations has long traditions. In 1942 King and Grover [22] and then Jessup [23] and Chumey et al. [24] used this method to explain the fact that the calculated heat capacity of a calorimetric bomb as the sum of the heat capacities of particular parts of the calorimeter was not equal to the experimentally determined heat capacity of the system. Since that time, many papers have been published on this field. For example, Zielenkiewicz et al. applied systems of heat balance equations for two and three distinguished domains [25 8] to analyze various phenomena occurring in calorimeters with a constant-temperature external shield Socorro and de Rivera [49] studied microeffects on the continuous-injection TAM microcalorimeter, while Kumpinsky [50] developed a method or evaluating heat-transfer coefficients in a heat flow reaction calorimeter. 

Urea, (NH2)2CO, is a commonly used fertihzer. When 237.1 mg of urea are burned, 2.495 kJ of heat are given off. When 1.000 g of urea is burned in a bomb calorimeter that contains 750.0 g of water, the temperature of the bomb and water increases by 1.23°C. What is the heat capacity of the bomb ... 

Bomb calorimeter. The heat flow, q, for the reaction is calculated from the temperature change multiplied by the heat capacity of the calorimeter, which is determined in a preliminary experiment... 

It is found that when 1.00 g of H2 is made to react completely with Cl2 in a bomb calorimeter, the temperature in the bomb (heat capacity = 9.33 kJ/°C) rises from 20.00°C to 29.82°C. How much heat is evolved by the reaction ... 

In earlier times, ethyl ether was commonly used as an anesthetic. It is, however, highly flammable. When five milliliters of ethyl ether, C HuQC/), (d - 0.714 g/mL) is burned in a bomb calorimeter, die temperature rises from 23-5°C to 39.7°Q The calorimeter heat capacity is 10.34 k)/°C. 

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