NH3 5.65 kJ/mol 28.9 J/mol•K 200 K

For ammonia (NH3),

the enthalpy of fusion is 5.65 kJ/mol and

the entropy of fusion is 28.9 J/mol•K.

a. Will NH3(s) spontaneously melt at 200. K?

b. What is the approximate melting point of ammonia?

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a. Will NH3(s) spontaneously melt at 200. K?

ΔG = ΔH – TΔS

( 참고 https://ywpop.tistory.com/7438 )

= (5650 J/mol) – [(200. K) (28.9 J/mol•K)]

= –130. J/mol

200. K에서 ΔG < 0 이므로,

NH3는 200. K에서 자발적으로 녹는다.

b. What is the approximate melting point of ammonia?

ΔG = ΔH – TΔS

ΔG = 0 인 온도를 계산하면,

0 = ΔH – TΔS

T = ΔH / ΔS

= 5650 / 28.9

= 195.5 K

답: 약 196 K

[키워드] ΔG = ΔH – TΔS 기준