The standard heat of combustion (AH°) of liquid 2,3,3-trimethylpentane [C8H18] is reported in a table of physical properties to be -4850 kJ/mol. A footnote indicates that the reference temperature for the reported value is 25°C and the presumed combustion products are CO2(g) and H2O(g).
- In your own words, briefly explain what all that means.
There is some question about the accuracy of the reported value, and you have been asked to determine the heat of combustion experimentally. You burn 2.010 grams of the hydrocarbon with pure oxygen in a constant-volume calorimeter and find that the net heat released when the reactants and products [CO2(g) and H2O(g)] are all at 25°C is sufficient to raise the temperature of 1.00 kg of liquid water by 21.34°C. Write an energy balance to show that the heat released in the calorimeter equals
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Chapter 9 Solutions
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- A bomb calorimetric experiment was run to determine the enthalpy of combustion of ethanol. The reaction is C2H5OH() + 3 O2(g) 2 CO2(g) + 3 H2O() The bomb had a heat capacity of 550 J/K, and the calorimeter contained 650 g of water. Burning 4.20 g of ethanol, C2HsOH() resulted in a rise in temperature from 18.5 C to 22.3 C. Calculate U for the combustion of ethanol, in kJ/mosl.arrow_forwardA 21.3-mL sample of 0.977 M NaOH is mixed with 29.5 mL of 0.918 M HCl in a coffee-cup calorimeter (see Section 6.6 of your text for a description of a coffee-cup calorimeter). The enthalpy of the reaction, written with the lowest whole-number coefficients, is 55.8 kJ. Both solutions are at 19.6C prior to mixing and reacting. What is the final temperature of the reaction mixture? When solving this problem, assume that no heat is lost from the calorimeter to the surroundings, the density of all solutions is 1.00 g/mL, the specific heat of all solutions is the same as that of water, and volumes are additive.arrow_forwardIn earlier times, ethyl ether was commonly used as an anesthetic. It is, however, highly flammable. When five milliliters of ethyl ether, C4H10O(l)(d=0.714g/mL), are burned in a bomb calorimeter, the temperature rises from 23.5C to 39.7C. The calorimeter contains 1.200 kg of water and has a heat capacity of 5.32 kJ/C. (a) What is qH2o? (b) What is qcal? (c) What is q for the combustion of 5.00 mL of ethyl ether? (d) What is q for the combustion of one mole of ethyl ether?arrow_forward
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