Understanding the definitions of heat and work.

Question

A mixture of gaseous reactants is put in to a cylinder, where a chemical reaction turns them in to gaseous products. The cylinder has a piston that moves in or out as necessary to keep a constant pressure on the mixture of 1 atm. The cylinder is also submerged in a large insulated water bath. 

From previous experiments, this chemical reaction is known to absorb 395. KJ of energy.

The position of the piston is monitored, and is determined from this data that the piston does 183. KJ of work on the system during the reaction.

 

1) is the reaction exothermic or endothermic?

2) does the piston move in, out, or neither?

3)does heat flow in to or out of the gas mixture?

4) how much heat flows?

Answer 1

1) The reaction is ENDOTHERMIC because it absorbs the heat.

2) Since it is observed that the piston does 183 kJ of work ON the system, it would be moving IN.  If the system was doing work on the surroundings, then the piston would be observed to move OUT.

3) Heat flows into the mixture because it says heat is absorbed, i.e. because it is endothermic.

4) 395 J flows in and 183 J flow out, so the net transfer of heat would be 395 - 183 = 212 J