In chemistry, potential energy is usually considered to be the energy . A. Stored in the surroundings.
B. Stored in an isolated system.
C. Energy gained by the Sun.
D. Stored in the chemical bonds.

Will you chech and finish these for me, because i am stumped with them.

Ammonia enters the expansion valve of a refrigeration system at a pressure of 10 bar and a temperature of 18oc and exits at 6.0 bar. the refrigerant undergoes a throttling process. determine the temperature, in oc, and the quality of the refrigerant at the exit of the expansion valve.

Does work output exceed work input when a machine is used? a) yes, it does, as machines create energy. b) it depends on the type of machine used. c) no, it doesn’t, as machines are inefficient. d) no, it doesn’t, as machines cannot create energy.