What mass of benzene, C6H6(l) must be burned Thermodynamic Data in a bomb calori

Question

What mass of benzene, C6H6(l) must be burned Thermodynamic Data in a bomb calorimeter to raise its temperature by 15 degree C? The principles of bomb calorimetry. (2) The meaning of heats of combustion. A bomb calorimeter is an insulated container that contains a reaction chamber designed to withstand high pressures. The reaction chamber, or bomb, is surrounded by water that absorbs the heat of the reaction. This experimental device is often used to study reactions at constant volume, particularly the combustion reactions of organic compounds. A sample of the compound being burned is placed in the reaction chamber that is then sealed and pressurized with oxygen. An electric current is passed through a thin wire that gets hot enough to initiate the combustion reaction. Heat is given off during the reaction and that heat is absorbed by the surroundings, causing the measured temperature of the water to rise. In this case, the heat capacity of the calorimeter is given, having been previously determined experimentally. This is called the calorimeter constant. It means that it takes 1.259 kJ of energy to raise the temperature of the reaction chamber's surroundings by one degree Celsius. The value of the heat of combustion is also given, showing that benzene will give off 4.19 kJ of heat energy for every gram of benzene burned. The heat lost by the benzene burning is equal to the heat gained by the surroundings, assuming no heat loss. Let x be the number of grams of benzene.

Explanation / Answer

Let X g be the required mass of benzene in the problem

now, 1 g of benzene on combustion gives 41.9 kJ of heat energy.

therefore X g og benzene will give of 41.9 x X kJ of heat energy

Again, the Calorimeter constant is 1.259 kJ/oC. ie, for increase in 1oC in temperature 1.259 kJ has to be absorbed

therefore for 15 oC rise in temperature, heat absorbed should be 15 x 1.259 kJ.

Now as per the problem this amount of heat is supplied by combustion of X g of benzene

hence,

- X x 41.9 kJ = + 15 x 1.259 kJ                     {NOTE -ve sign for heat evolved and +ve sign for heat absorbed}

or X x 41.9 kJ + 15 x 1.259 kJ  = 0

This is how the equation in the second picture has come.

Related Questions

Navigate

• Browse (All)
• Browse W
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.