燃烧热计算公式

燃烧热计算公式

已知：Qv苯甲酸=—26581 J/g，Q点火丝=—1400 J/g，

M苯甲酸=122.12g/mol, M萘=128.11g/mol

—m苯甲酸·Qv苯甲酸—m点火丝·Q点火丝=（m水C水+C计）·⊿T苯甲酸

—m苯甲酸·Qv苯甲酸—m点火丝·Q点火丝= C总·⊿T苯甲酸

（3）计算

word/media/image1.gif通过标准样品苯甲酸的数据求总的热容C总（J/K）

—m苯甲酸·Qv苯甲酸—m点火丝·Q点火丝 = C总·⊿T苯甲酸

—0.9945g × (—26581J/g) — 0.004g × (—1400J/g) = C总×2.033K

C总=cfbdc166a55403ca04249dc6c5c79435.png

=933227130199273c450882375ec95100.png

=11480.85J/K

②通过总的热容C总（J/K）求萘的恒容燃烧热Qv萘

—m萘·Qv萘—m点火丝·Q点火丝 = C总·⊿T萘

—1.1213g ×Qv萘 — 0.0048g × (—1400J/g) = 11480.85J/K × 3.56K

—1.1213g ×Qv萘＋6.72J = 40871.83J

Qv萘 = 1d61d820ae8043029a9e6abed207cfc6.png

= —36444.40J/g

J/g × g/mol = J/mol

= —36444.40J/g× 128.11g/mol

= —4668.89 KJ/mol

word/media/image5.gif求萘的恒压燃烧热

cc3c4185ea03e4d3870600d17d591abb.png ∆n= -2

QP = QV + ∆nRT

= -4668.89 KJ/mol + (-2)⨯8.314J/mol/K⨯298K/1000

= -4673.85kJ⋅mol-1

word/media/image7.gif误差估算

371c19ef93abb27c0b7526bad7653530.png

（4）另一种计算方式。所有燃烧热的值都取正值！

word/media/image1.gif通过标准样品苯甲酸的数据求总的热容C总（J/K）

m苯甲酸·Qv苯甲酸 ＋ m点火丝·Q点火丝 = C总·⊿T苯甲酸

0.9945g × 26581J/g ＋ 0.004g × 1400J/g = C总×2.033K

C总=d8fbc68f77b035cfbada6ae893f1513e.png

=933227130199273c450882375ec95100.png

=11480.85J/K

②通过总的热容C总（J/K）求萘的恒容燃烧热Qv萘

m萘·Qv萘 ＋ m点火丝·Q点火丝 = C总·⊿T萘

1.1213g ×Qv萘＋ 0.0048g × 1400J/g = 11480.85J/K × 3.56K

1.1213g ×Qv萘＋6.72J = 40871.83J

Qv萘 = 6186145e16e725a211a007aa34d99502.png

= 36444.40J/g

J/g × g/mol = J/mol

= 36444.40J/g× 128.11g/mol

= 4668.89 KJ/mol

word/media/image5.gif求萘的恒压燃烧热

cc3c4185ea03e4d3870600d17d591abb.png ∆n= -2

QP = QV + ∆nRT

= 4668.89 KJ/mol + 2⨯8.314 J/mol/K ⨯298K/1000

= 4673.85kJ⋅mol-1

word/media/image11.gif误差估算

371c19ef93abb27c0b7526bad7653530.png

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