Question

A gas expands from 3 dm³ to 5dm³ against a constant pressure of 3atm . The work done during expansions is used to heat 50 moles of water of temperature 290k calculate and find temp of water (sp heat of water=4.184Jg^-1 K)

Answer 1

$$\begin{gathered} Workdoneagainstcons\tan texternalpressureforanirreversibleprocess \\ W=-P∆V \\ ∆V=5-3=2d{m}^3=2\times {10}^{-3}{m}^3 \\ P=3atm=3\times 1.013\times {10}^{5}N{m}^{-2} \\ W=-3\times 1.013\times {10}^{5}2\times {10}^{-3}=-607.8J \\ Thisworkenergyisusedinheatingwater \\ -W=q=n\times C\times ∆T \\ 607.8=10\times 4.184\times 18\times ∆T \\ ∆T=0.81 \\ Finaltemperature=290+0.81K=290.81K \end{gathered}$$