Anybody could help me out?

Which symbol can be used to indicate the pressure at which a chemical reaction is carried out? 25°c 2 atm pa

Give one example of a pure (exact) number and of an estimated (measured) number.

How long could you survive without electricity? what parts of your life would be affected by loss of electricity? should you prepare for an electricity outage, and if so, how would you prepare? what backup system could your family or community install to generate limited amounts of electricity during an outage? how does this system create an electric force field and generate electric current?