The air in an inflated balloon (the system) absorbs 125 J of heat from its proximity to a fire. The balloon expands and does 85 KJ of work. What is the change in internal energy (in kJ) (AU) for the system? Respond with the correct number of significant figures in scientific notation (Use E notation and only 1 digit before decimal e.g. 2.5E5 for 2.5 x 105) Type your numeric answer and submit Hint You'll need to use Equation 5.13 in Section 5.3. Cannot be empty X

The air in an inflated balloon (the system) absorbs 125 J of heat from its proximity to a fire. The balloon expands and does 85 KJ of work. What is the change in internal energy (in kJ) (AU) for the system? Respond with the correct number of significant figures in scientific notation (Use E notation and only 1 digit before decimal e.g. 2.5E5 for 2.5 x 105) Type your numeric answer and submit Hint You'll need to use Equation 5.13 in Section 5.3. Cannot be empty X

Chemistry by OpenStax (2015-05-04)

1st Edition

ISBN:9781938168390

Author:Klaus Theopold, Richard H Langley, Paul Flowers, William R. Robinson, Mark Blaser

Publisher:Klaus Theopold, Richard H Langley, Paul Flowers, William R. Robinson, Mark Blaser

Chapter5: Thermochemistry

Section: Chapter Questions

Problem 38E: Which is the least expensive source of energy in kilojoules per dollar: a box of breakfast cereal...

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Given the following (hypothetical) thermochemical equations: A+B2C;H=447kJA+3D2E;H=484kJ2D+B2F;H=429kJ Calculate H, in kJ, for the equation 4E+5B4C+6F
A gas is cooled and loses 82 J of heat. The gas contracts as it cools, and work done on the system equal to 29 J is exchanged with the surroundings. What are q, w, and U?
Natural gas companies in the United States use the therm as a unit of energy. One therm is 1105 BTU. (a) How many joules are in one therm? (1J=9.48104BTU) (b) When propane gas, C3H8, is burned in oxygen, CO2 and steam are produced. How many therms of energy are given off by 1.00 mol of propane gas?
The complete combustion of acetylene, C2H2(g), produces 1300. kJ of energy per mole of acetylene consumed. How many grams of acetylene must be burned to produce enough heat to raise the temperature of 1.00 gal water by 10.0c if the process is 80.0% efficient? Assume the density of water is 1.00 g/cm3
A 45-g aluminum spoon (specific heat 0.88 J/g C) at 24 C is placed in 180 mL (180 g) of coffee at 85 C and the temperature of the two become equal. (a) What is the final temperature when the two become equal? Assume that coffee has the same specific heat as water. (b) The first time a student solved this problem she got an answer of 88 C. Explain why this is clearly an incorrect answer.
Which is the least expensive source of energy in kilojoules per dollar: a box of breakfast cereal that weighs 32 ounces and costs $4.23, or a liter of isooctane (density, 0.69 19 g/mL) that costs $0.45? Compare the nutritional value of the cereal with the heat produced by combustion of the isooctane under standard conditions. A 1.0-ounce serving of the cereal provides 130 Calories.
In the 1880s, Frederick Trouton noted that the enthalpy of vaporization of 1 mol pure liquid is approximately 88 times the boiling point, Tb, of the liquid on the Kelvin scale. This relationship is called Troutons rule and is represented by the thermochemical equation liquid gas H = 88 Tb, joules Combined with an empirical formula from chemical analysis, Troutons rule can be used to find the molecular formula of a compound, as illustrated here. A compound that contains only carbon and hydrogen is 85.6% C and 14.4% H. Its enthalpy of vaporization is 389 J/g, and it boils at a temperature of 322 K. (a) What is the empirical formula of this compound? (b) Use Troutons rule to calculate the approximate enthalpy or vaporization or one mole of the compound. Combine the enthalpy of vaporization per mole with that same quantity per gram to obtain an approximate molar mass of the compound. (c) Use the results of parts (a) and (b) to find the molecular formula of this compound. Remember that the molecular mass must be exactly a whole-number multiple of the empirical formula mass, so considerable rounding may be needed.
9.104 An engineer is using sodium metal as a cooling agent in a design because it has useful thermal properties. Looting up the heat capacity, the engineer finds a value of 28.2 J mol-l °C-l. Carelessly, he wrote this number down without units. As a result, it was later taken as specific heat. (a) What would he the difference between these two values? (b) Would the engineer overestimate the ability of sodium to remove heat from the system or underestimate it because of this error? Be sure to explain your reasoning.
The Group 2A carbonates decompose when heated. For example, BaCO3(s)BaO(s)+CO2(g) Use enthalpies of formation (see Appendix C) and calculate the heat required to decompose 6.50 g of barium carbonate.
You drink 350 mL of diet soda that is at a temperature of 5 C. (a) How much energy will your body expend to raise the temperature of this liquid to body temperature (37 C)? Assume that the density and specific heat capacity of diet soda are the same as for water. (b) Compare the value in part (a) with the caloric content of the beverage. (The label says that it has a caloric content of 1 Calorie.) What is the net energy change in your body resulting from drinking this beverage? (1 Calorie = 1000 kcal = 4184 J.) (c) Carry out a comparison similar to that in part (b) for a nondiet beverage whose label indicates a caloric content of 240 Calories.