Which of the following observations would indicate that a material is a pure substance

Large helium-filled balloons are used to lift scientific equipment to high altitudes. what is the pressure inside such a balloon if it starts out at sea level with a temperature of 10.0ºc and rises to an altitude where its volume is twenty times the original volume and its temperature is – 50.0ºc ?

3. consider a process in which a gas with the properties of air expands at constant pressure as described by the cups of air discussion in class. one kilogram of air starts out at 1 atm and 290 k. the air expands its volume by absorbing a sufficient amount of thermal energy to increase the temperature at constant pressure to 350 k. a. on a p-v diagram, sketch this process with point a as the starting point and point b as the ending point. b. if the process is completely reversible, calculate the thermal energy added from an external source. c. calculate the entropy change for this process assuming it is reversible. d. calculate the work delivered externally if this is a reversible process. e. if the process is completely irreversible, calculate the amount of entropy change for the process that is due to irreversibilities. f. if the process is completely irreversible, calculate the amount of thermal energy added from an external source and compare this result to the thermal energy calculated in part b. g. for the completely irreversible process, calculate the entropy change due to this thermal energy addition. h. for the completely irreversible process, calculate the total entropy change and compare it to the entropy change in part c.

Select the correct answer from each drop-down menu. in a reversible reaction, the forward reaction takes place the reverse reaction. such a reaction, on reaching equilibrium, will have .