0.0℃ 1.00 atm 39.1 mol He volume 876 L 38.0℃ 998 L q w ΔE 20.8 J/℃

0.0℃ 1.00 atm 39.1 mol He volume 876 L 38.0℃ 998 L q w ΔE 20.8 J/℃

 

 

A balloon filled with 39.1 moles of helium

has a volume of 876 L at 0.0℃ and 1.00 atm pressure.

At constant pressure, the temperature of the balloon is increased to 38.0℃,

causing the balloon to expand to a volume of 998 L.

Calculate q, w, and ΔE for the helium in the balloon.

The molar heat capacity for helium gas is 20.8 J/℃•mol.

 

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q = C m Δt ... 비열인 경우,

( 참고 https://ywpop.tistory.com/2897 )

 

 

q = C n Δt ... 몰열용량인 경우

= (20.8 J/mol•℃) (39.1 mol) (38.0 – 0.0 ℃)

= 30904.64 J

= 30.9 kJ

 

 

 

w = –PΔV

= (1.00 atm) (998 – 876 L)

= –122 atm•L

 

 

 

1 atm•L = 101.325 J 이므로,

( 참고 https://ywpop.tistory.com/6646 )

 

–122 atm•L × (101.325 J / 1 atm•L)

= –12361.65 J

= –12.4 kJ

 

 

 

ΔE = q + w

( 참고 https://ywpop.tistory.com/7219 )

 

= (30.9 kJ) + (–12.4 kJ)

= 18.5 kJ

 

 

 

 

[키워드] calc q w ΔE 기준문서, q = nCΔt 기준문서, q = CnΔt 기준문서, ΔE = q + w 기준문서, atm L J 기준문서