Oxygen gas can be prepared by heating potassium chlorate according to the following equation:

2KClO3(s) → 2KCl(s) + 3O2(g)

The product gas, O2, is collected over water at a temperature of 20 °C and a pressure of 747 mm Hg. If the wet O2 gas formed occupies a volume of 6.42 L, the number of grams of O2 formed is g. The vapor pressure of water is 17.5 mm Hg at 20 °C.

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.