Consider isobaric process of 0.4moles of ideal gas from 22.4l and 1 atm to 10.5l. Given that Cp for the gas is 5/3R. Calculate.∆t ,W ,∆E and ∆H

Are you sure Cp is 5/3 R? Perhaps 5/2 R.

W= -pdV and solve for W.
W = nRdT Knowing W solve for dT

dH = nCpdT Solve for dH
dE = dH + W
Post your work if you get stuck.