Analysis of an unknown element by mass spectrometry determines that 59.0% of the sample has an atomic mass of 79.0 amu, while the remainder has a mass of 81.0 amu. What is the average atomic mass of this unknown substance?

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   

Qand k are only the same when the forward rate of the reaction has reached zero.

The answer is c.  h+  and oh−  react to form water (h2o). i just took the test and i got it right. hope this !