Short answer=depends. If you never had it and are in the same room with an active case for half an hour,you will get it within 10-21 days.If you had it as a kid, you are immune.Most who can't remember are immune (96%).It is nasty if you get it as an adult (can be fatal).
It depends. It depends on your immunization status (there is a childhood vaccine for chickenpox now), and your exposure (the people around you). If you are unimmunized and never had exposure to the illness, exposure as an adult will likely result in chickenpox. Most unimmunized adults were exposed as children and developed natural immunity without knowing it.