A mixture of gaseous reactants is put into a cylinder, where a chemical reaction

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 and out, as nesscary, to keep constant pressure on the mixture at 1 atm. The cylinder is also submerged in a large insulated water bath. From previous experiments, this chemical reaction is known to absorb 248 kJ of engery. The postion of the piston is monitord and it is determined from this data that the piston does 144 kJ of work done on the system during the reaction. Is the reaction exothermic or endothermic? Does the temperature of the water go up or down? Does the piston move in or out? Does does heat flow in or out of the gas mixture? How much heat flows (answer in kJ)?

Explanation / Answer

As the heat is absorbed by the reaction mixture this implies that the reaction is occurring by absorbing heat and this occurred in the endothermic reaction .

As the reaction is endothermic and heat is given to the system so gases expend because pressure is kept constant and the pistin moves out

Total heat absorbed by the reaction mixture is 248 kJ

Work done on the system is 144kJ

So the rest of the heat is provided by the surroundings

The surrounding of the system is occupied by water so rest of the heat required for reaction is absorbed from water so the temperature of water decreases.

Rest of the heat required is = 248-144 = 104kJ

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