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. (See sketch at right.) From previous experiments, this chemical reaction is known to release 223.kJ of energy. The temperature of the water bath is monitored, and it is determined from this data that 173.kJ of heat flows out of the system during the reaction. Does the temperature of the water bath go up or down?
Does the piston move in or out?
Does heat flow into or out of the gaseous mixture?
How much heat flows?
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From the question, it is noted that 173.kJ of heat flows out of the system into the insulated water bath therefore the temperature of the water bath goes up
as seen in the relation ΔH = m·c·ΔT
Where ΔH heat measured by temperature rise ΔT of a given mass of water m of specific heat capacity of 4.2 J/g°C
The amount of heat measured from previous experiment is more than the heat from the present reaction therefore since in the present reaction is constant pressure and from the first law of thermodynamics Energy can neither be created nor destroyed, the balance heat will be transformed to work evidence in the piston moving out
ΣH = Q + W where
w = P × ΔV = P × (P₂ - P₂)
Heat flows out of the gaseous mixture and is sensed from the rise in the temperature of the water bath
