How is it possible for an endothermic reaction to be spontaneous?

What is the molar mass of a gas that has density of 2.054 g/l

Draw the structure for 5-isopropyl-2-methyl-3-nonene

Equal numbers of moles of he(g), ar(g), and ne(g) are placed in a glass vessel at room temperature. if the vessel has a pinhole-sized leak, which of the following will be true regarding the relative values of the partial pressures of the gases remaining in the vessel after some of the gas mixture has effused?