22.55% phosphorus and 77.45% chlorine what is the empirical formula

What is the chemical formula of the following compound

Harvey kept a balloon with a volume of 348 milliliters at 25.0˚c inside a freezer for a night.  when he took it out, its new volume was 322 milliliters, but its pressure was the same.  if the final temperature of the balloon is the same as the freezer’s, what is the temperature of the freezer? the temperature of the freezer is  kelvins.

Which one of the following bonds would you expect to be the most polar? a) b–h b) n–h c) p–h d) al–h e) c–h