2. (3points, Chapter 2, Problem 2.23) The composition of dry air at sealevel is 78.03% N2, 20.99% O2, and 0.033% CO2by volume. (a) Calculate the average molar mass of this air sample. (b) Calculate the partial pressure of N2, O2, and CO2in atm. (Hint: At constant temperature and pressure, the volume of a gas is directly proportional to the number of moles of the gas. Thus, % by volume

Nebulae are enormous clouds in outer space. they are made mostly of hydrogen gas, helium gas, and dust. some nebulae glow brightly, while others do not. the stars that people see are huge, bright balls of glowing gas. they are made mostly of hydrogen and helium. which statement correctly describes other ways in which nebulae and stars are different? a. stars can form inside a nebula but a nebula can never be produced by any star. b. a star always has a higher density than a nebula. c. stars can never form inside a nebula but a nebula can be produced by any star. d. a nebula always has a higher density than a star.