Change in enthalpy (4C.3)

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Amy Luu 2G
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Joined: Wed Sep 18, 2019 12:19 am

Change in enthalpy (4C.3)

Postby Amy Luu 2G » Tue Feb 11, 2020 2:46 pm

Calculate the final temperature and the change in enthalpy when 765 J of energy is transferred as heat to 0.820 mol Kr(g) at 298 K and 1.00 atm (a) at constant pressure; (b) at constant volume. Treat the gas as ideal.
I know how to find the final temperature but I am having trouble finding the change in enthalpy. For part a) i thought since the system was under constant pressure, the change in enthalpy would equal q. Is this correct? If not what equation can I use. I am unsure how to find the change in enthalpy of part b too

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Re: Change in enthalpy (4C.3)

Postby AArmellini_1I » Tue Feb 11, 2020 5:06 pm

For constant pressure q = delta H not delta S. So you would use delta S = q/T or delta H / T (you may also be able to use delta S = -n R ln (V2/V1)?
For constant volume you also still use q/T but couldn't use S = -n R ln (V2/V1)
If the system is isothermal use delta S = n C ln (T2/T1)

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