of gaseous reactants is put into a cylinder, where a reaction into gaseous products. The cylinder has a piston that moves in or out, as necessary, to keep a constant pressure on the mixture of 1 atm. The cylinder is also submerged in a large insulated water bath. (See sketch at right.) From previous experiments, this chemical reaction is known to release 126. kJ of energy. The position of the piston is monitored, and it is determined from this data that the system does 118. kJ of work on the piston during the reaction. exothermic Is the reaction exothermic or endothermic? endothermic up Does the temperature of the water bath go up or down? down neither in Does the piston move in or out? out neither

Every day a certain amount of water evaporates from Earth’s oceans, lakes, and land surface and forms water vapor and clouds in the atmosphere. Every day a certain amount of rain falls back to Earth. Make the reasonable assumption that, on average, the energy absorbed by the evaporation and lifting of the water is equal to the energy released by its condensation and falling back to earth. The evaporation of one mole of water requires approximately 40.6×103 J of heat. An equal amount of heat is released when a mole of water condenses. The annual volume of rainfall on Earth is approximately 4.9×105 km3 and the average cloud altitude is 8.9 km above Earth’s surface. How much energy, in joules, is required every day to evaporate and lift the water?

21 Consider the combustion of in oxygen gas to produce carbon dioxide gas and water vapor. In an experiment, 0.1063 g of C₅H₈ is combusted to produce enough heat to raise the temperature of 150.0 g of water by 7.632 °C. C₅H₈ (l) + 7 O₂ (g) → 5 CO₂ (g) + 4 H₂O (g) d If 4790 J of heat were absorbed by the water, then how much heat, in J, was produced by the combustion of C₅H₈? (include the appropriate sign)

A sample of gass occupies a volume of 56.4mL. As it expands, it does 133.3J of work on its surroundings at a constant pressure of 783 torr. What is the final volume of gas?