MIXTURE Reactants

Question

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

The cylinder is also submerged in a large insulated water bath.

The temperature of the water bath is monitored, and it is determined from this data that 245.kJ

of heat flows out of the system during the reaction. The position of the piston is also monitored, and it is determined from this data that the system does 395.kJ of work on the piston during the reaction.

1. Is the reaction endo- or exo- thermic?
2. Does the temp. of the water bath go up or down?
3. Does the piston move in or out?
4. Does the reaction absorb or release energy?
5. How much energy does the reaction absorb or release? Be sure your answer has the correct number of significant digits.

Answer 1

The reaction is exothermic as energy flows out of the system.

The temperature of the water goes up.

The piston moves out.

The reaction releases energy.

Energy released is 245. kj + 395. kj = 640. kj