Karen measures the initial volume of water as 12.5 mL. She then adds a 2.3 gram rubber stopper and the volume rises to 20.8 mL. What is the volume of Karen's rubber stopper? HELPPLEASE

It takes 945.kj/mol to break a nitrogen-nitrogen triple bond. calculate the maximum wavelength of light for which a nitrogen-nitrogen triple bond could be broken by absorbing a single photon.

Analyze how limestone is weathered and identify the features that are formed as a result of this dissolution

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.