1. Determine the total pressure of a gas mixture that contains oxygen at a pressure of 150 mmHg, nitrogen at 350.mmHg pressure, and helium at a pressure of 200 mmHg.

The most plausible answer is b, duration. the given amount of time is considered how long it last for.

Ch4 and ph3 are both covalent since they are composed both of non-metals.    ch4 is non- polar because of  london forces and has a geometry of tetrahedral  ph3 , on the other hand, is umbrella shaped polar and has dipole-dipole intermolecular force (imf) . since ph3 is polar, it has a stronger imf