1. Ethanol, C2H6O, is most often blended with gasoline - usually as a 10 per cen
ID: 1006375 • Letter: 1
Question
1.
Ethanol, C2H6O, is most often blended with gasoline - usually as a 10 per cent mix - to create a fuel called gasohol. Ethanol is a renewable resource and ethanol-blended fuels, like gasohol, appear to burn more efficiently in combustion engines. The heat of combustion of ethanol is 326.7 kcal/mol.
The heat of combustion of 2-methylheptane, C8H18, is 1.306×103 kcal/mol. How much energy is released during the complete combustion of 394 grams of 2-methylheptane ?
_______kcal
Assuming the same efficiency, would 394 grams of ethanol provide more, less, or the same amount of energy as 394 grams of 2-methylheptane?
_________
more or
less or
the same amount
2.
Combustion reactions are exothermic. The heat of reaction for the combustion of 2-methylhexane, C7H16, is 1.150×103 kcal/mol. What is the heat of combustion for 2-methylhexane in kcal/gram?
______kcal/gram
How much heat will be given off if molar quantities of 2-methylhexane react according to the following equation?
C7H16 + 11 O2 7 CO2 + 8 H2O
______kcal
3.
A bomb calorimeter, or constant volume calorimeter, is a device often used to determine the heat of combustion of fuels and the energy content of foods.
Since the "bomb" itself can absorb energy, a separate experiment is needed to determine the heat capacity of the calorimeter. This is known as calibrating the calorimeter.
In the laboratory a student burns a 1.00-g sample of glutaric acid (C5H8O4) in a bomb calorimeter containing 1060. g of water. The temperature increases from 24.90 °C to 28.00 °C. The heat capacity of water is 4.184 J g-1°C-1.
The molar heat of combustion is ?2151 kJ per mole of glutaric acid.
C5H8O4(s) + 5 O2(g) 5 CO2(g) + 4 H2O(l) + Energy
Calculate the heat capacity of the calorimeter.
heat capacity of calorimeter = ________J/°C
4.
A bomb calorimeter, or a constant volume calorimeter, is a device often used to determine the heat of combustion of fuels and the energy content of foods.
In an experiment, a 0.4472 g sample of benzil (C14H10O2) is burned completely in a bomb calorimeter. The calorimeter is surrounded by 1.121×103 g of water. During the combustion the temperature increases from 23.27 to 25.82 °C. The heat capacity of water is 4.184 J g-1°C-1.
The heat capacity of the calorimeter was determined in a previous experiment to be 761.6 J/°C.
Assuming that no energy is lost to the surroundings, calculate the molar heat of combustion of benzil based on these data.
C14H10O2(s) + (31/2) O2(g) 5 H2O(l) + 14 CO2(g) + Energy
Molar Heat of Combustion = _______ kJ/mol
Explanation / Answer
Post one more question to get the remaining answers
1) Molar mass of 2-methyl heptane = 8 * 12 + 18 * 1
=> 96 + 18
=> 114 gm/mol
Number of moles of 2-methyl heptane in 394 grams = 394/114 = 3.4561 moles
Energy Released = 1306 kcal/mol * 3.4561 mol = 4513.7192 kCal
Molar mass of ethanol = 24 + 6 + 16 = 46 gm/mol
Number of moles of ethanol in 394 grams = 394/46 = 8.565 moles
Energy released will be lesser in the case of ethanol as compared to 2-methyl heptane
2)
Combustion reactions are exothermic. The heat of reaction for the combustion of 2-methylhexane, C7H16, is 1.150×103 kcal/mol. What is the heat of combustion for 2-methylhexane in kcal/gram?
Molar mass of C7H16 = 7 * 12 + 16 * 1 = 100 gm/mol
Heat of combustion = 11.50 kcal/gm
How much heat will be given off if molar quantities of 2-methylhexane react according to the following equation?
C7H16 + 11 O2 7 CO2 + 8 H2O
Heat of reaction = 2 * molar heat of combustion of 2-methyl hexane
=> 2 * 1.150 * 10^3 Kcal
=> 2300 kCal
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