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If the heat capacity varies with temperature, a better form of equation 2.9 is to solve
A 50.0-g sample of white phosphorus is heated from 298 K to 350K. If its molar heat capacity is
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Physical Chemistry
- Benzoic acid, C6H5COOH, is a common standard used in bomb calorimeters, which maintain a constant volume. If 1.20 g of benzoic acid gives off 31, 723 J of energy when burned in the presence of excess oxygen and in a water bath having a temperature of 24.6 C, calculate q, w, H, and U for the reaction.arrow_forwardThe following are values of heat capacity for nitrogen gas; Temp K Cv J/mol. K 300 20.8 400 20.9 500 21.2 600 21.8 700 22.4 800 23.1 900 23.7 1000 24.3 1100 24.9 Using the general formula Cv = A BT C/T2, find values of A, B, and C that fit the given data.arrow_forwardThe enthalpy of combustion of diamond is -395.4 kJ/mol. C s, dia O2 g CO2 g Determine the fH of C s, dia.arrow_forward
- A sample of ethanol, C2H5OH, weighing 2.84 g was burned in an excess of oxygen in a bomb calorimeter. The temperature of the calorimeter rose from 25.00C to 33.73C. If the heat capacity of the calorimeter and contents was 9.63 kJ/C, what is the value of q for burning 1.00 mol of ethanol at constant volume and 25.00C? The reaction is C2H5OH(l)+3O2(g)2CO2(g)+3H2O(l) Is q equal to U or H?arrow_forwardThe octane number of gasoline is based on a comparison of the gasolines behavior with that of 2,2,4-trimethylpentane, C8H18(), which is arbitrarily assigned an octane number of 100. The standard enthalpy of combustion of this compound is 5456.6 kJ/mol. (a) Write the thermochemical equation for the combustion of 2,2,4-trimethylpentane. (b) Use the standard enthalpies of formation in Appendix G to calculate the standard enthalpy of formation of 2,2,4-trimethylpentane.arrow_forwardNitrogen gas (2.75 L) is confined in a cylinder under constant atmospheric pressure (1.01 105 pascals). The volume of gas decreases to 2.10 L when 485 J of energy is transferred as heat to the surroundings. What is the change in internal energy of the gas?arrow_forward
- Assume that 1.20 g of benzoicacid, C6H5COOH, is burned in a porcelain dish exposed to the air.If 31, 723 J of energy is givenoff andthe surrounding temperature is 24.6C, calculate q, w, H,and U. Compare your answers to those from the previousproblem.arrow_forwardA sample of benzene, C6H6, weighing 3.51 g was burned in an excess of oxygen in a bomb calorimeter. The temperature of the calorimeter rose from 25.00C to 37.18C. If the heat capacity of the calorimeter and contents was 12.05 kJ/C, what is the value of q for burning 1.00 mol of benzene at constant volume and 25.00C? The reaction is C6H6(l)+152O2(g)6CO2(g)+3H2O(l) Is q equal to U or H?arrow_forwardWhen 1.000 g of ethylene glycol, C2H6O2, is burned at 25C and 1.00 atmosphere pressure, H2O(l) and CO2(g) are formed with the evolution of 19.18 kJ of heat. a Calculate the molar enthalpy of formation of ethylene glycol. (It will be necessary to use data from Appendix C.) b Gf of ethylene glycol is 322.5 kJ/mol. What is G for the combustion of 1 mol ethylene glycol? c What is S for the combustion of 1 mol ethylene glycol?arrow_forward
- A 220-ft3 sample of gas at standard temperature and pressure is compressed into a cylinder, where it exerts pressure of 2000 psi. Calculate the work (in J) performed when this gas expands isothermally against an opposing pressure of 1.0 atm. (The amount of work that can be done is equivalent to the destructive force of about 1/4 lb of dynamite, giving you an idea of how potentially destructive compressed gas cylinders can be if improperly handled!)arrow_forwardCalculate the specific heat of a material if 288J of energy were required to heat 50.5g of the material from 298K to 330K. What are the units?arrow_forwardWhat is the change in internal energy when a gas contracts from 377mL to 119mLundera pressure of 1550 torr, whileat the same time being cooled by removing 124.0J ofheat energy?arrow_forward
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