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第二章 化学反应的基本原理 PowerPoint PPT Presentation


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第二章 化学反应的基本原理. 教学内容 § 2.1 热化学与能量 § 2.2 化学反应进行的方向 § 2.3 化学反应的限度和化学平衡 § 2.4 化学反应速率. § 2.1 热化学与能量. 化学反应是反应物分子中旧键的削弱或断裂,产物分子中新键形成的过程。旧键削弱或断裂需要吸收能量。新键形成要释放能量,因而,在化学反应过程中,不仅发生物质的质变,而且总是伴随有能量的吸收和放出。 化学反应过程中可以放热或吸热,这是常见的化学能与热能的变化。化学反应所释放的热量是日常生活和生产所需能量的主要来源之一。.

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第二章 化学反应的基本原理

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2.1

2.2

2.3

2.4


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2.1


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CH4 +2O2CO2 + 2H2O(l)

H 298= -890.45 kJ

C12H20O11(s) + 12O2 = 12CO2 + 11H2O

H 298= -1965 kJ

CaCO3(s) = CaO(s) + CO2

H 298= 177.8 kJ


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2 1 1

2.1.1


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(open system)

(closed system)

(isolated system)


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2 .

n = 1 mol p = 1.013105 Pa V = 22.4 L T = 273 Kn,p,VT


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1

2


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1.

2.

3.


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.


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298K, H2Og)

1

298K,H2O(l) 373K,H2Og)

373K,H2O(l)

2


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p


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p1=1.01105Pa

T1=298K

p2=2.02105Pa

T1=298K

p1=1.01105Pa

T2=398K

p2=2.02105Pa

T2=398K


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4.


2 1 2

2.1.2

Q( J )

W( J )


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Q

W


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  • (1)

  • (2)


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p

W = F l

= pS (l2 - l1)

= p(S l2 - Sl1)

= pV

,,W, W - ,

W = -pV

V

T


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U

U


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QWU

U = Q + W


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1100 kJ200 kJ

U Q + W

U 100 + (- 200) - 100 kJ

U = U

U = 100 kJ


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2 1 3

2.1.3

V = 0 W = -pV = 0

rU = Qv + W = Qv

rU = Qv

Qv


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p = 0

rU = Qp + W

= Qp p V

= Qp ( pV )

Qp = rU + ( pV )


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Qp = ( U2U1 ) + ( p2V2 p1V1 )

= ( U2 + p2V2 ) ( U1 + p1V1 )

= ( U + pV )

Qp = ( U + pV )

UpV U + pV

H = U + pV H

Qp = rH

Qp


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  • ()QpQv

  • QpH

  • H = Qp

  • H J kJ

  • H <0

  • H >0


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QvQp

Qp - Qv = Hp -Uv = (Up + pV)-Uv

U Up = Uv

pV = nRT

n

Qp- Qv = nRT


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  • 1 mol

  • Qp,m - Qv,m=n(m)RT

  • n(m)


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2298K 6.5 g 272.3 kJ rUmrHm


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C6H6l7.5O2g6CO2g3H2Ol

rUm272.36.5/78

=3267.6 kJmol-1

rHm rUm vB(g)RT

3267.667.58.31429810-3

3270.1 kJmol-1


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3 298KHgO 22.7 kJ Hgl50.10 grHmHgl


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HgO(s)Hg(l) + 1/2O2(g)

rHm 22.750.10/200.59

90.89 kJmol-1

rHm rUm vB(g)RT

rUm rHm vB(g)RT

90.890.58.31429810-3

89.65 kJmol-1

Q89.6550.10200.5922.4 kJmol-1


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1

aA + dD = gG + hH

t=0 nA(0) nD(0) nG(0) nH(0)

t nA(t) nD (t) nG(t) nH (t)


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: t ( ksai )

mol


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3H2 + N2 = 2NH3

t=0 3 mol 1 mol 0

t 0 0 2 mol

3/2H2 + 1/2N2 = NH3

t=0 3 mol 1 mol 0

t 0 0 2 mol


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2

(1)

(2) rHm

(3)


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s (solid)l (liquid), g (gas)

298 K 1.013 10 5 Pa


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1 rHmr (reaction) m = 1 mol


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  • Xi = 1

  • A:

    mA = 1 mol.kg-1 m

  • 1.013105 Pa


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C () + O2 (g) CO2 (g) rHm= 393.5 kJ/mol (1)

C () + O2 (g) CO2 (g) rHm = 395.4 kJ/mol (2)

H2 (g) + 1/2 O2 (g) H2O (g) rHm = 241.8 kJ/mol (3)

H2 (g) + 1/2 O2 (g) H2O (l) rHm = 285.8 kJ/mol (4)

2H2 (g) + O2 (g) 2 H2O (l) rHm = 571.6 kJ/mol (5)

H2O (g) H2 (g) + 1/2 O2 (g) rHm = + 241.8 kJ/mol (6)

rHm > 0 rHm < 0

( 1 ) ( 2 )

( 3 ) ( 4 )

( 4 ) ( 5 )

( 3 ) ( 6 )


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(1)+(2)=(3)

Qp(1) + Qp(2) = Qp(3)

rHm(1) + rHm (2) = rHm (3)

(1) - (2) = (3)

Qp(1) - Qp(2) = Qp(3)

rHm(1) - rHm(2) = rHm(3)


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1

H2(g) + O2(g)

2

2H(g) + O(g)

rH

H2O(l)

rH3

rH1

rH2

H2O(g)

rH = rH1 + rH2 + rH3


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  • Hess G H1802-1850,1840


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4 (1) C() + O2(g) CO2(g)

rHm = -393.5 kJ.mol-1

(2) CO(g) + 1/2 O2(g) CO2(g)

rHm = -282.9 kJ.mol-1

(3)C() + 1/2O2(g) = CO (g)

rHm =


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C() + O2(g)

CO2(g)

rHm (2)

rHm(3)=

rHm(1)

CO(g) + 1/2 O2(g)

<3> =<1> - <2>

rHm(3)=rHm(1)-rHm(2)= -393.5 + 282.9 = -110.6 kJmol-1


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fHmJ/mol

fHm= 0

fHm = rHm

1 mol


F h m

fHm

  • fHm(kJ.mol-1)

  • C()+1/2O2(g)=CO (g) -110.53

  • C()+O2 (g)=CO2 (g) -393.51

  • H2 (g)+1/2O2 (g)=H2O(l) -285.84

  • H2 (g)+1/2O2 (g)=H2O(g) -241.82

  • 1/2H2 (g)+1/2Cl2 (g)=HCl (g) -92.31

  • C()=C() 1.987

  • C()=C() 0


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H

rHm

rHm(T)T

fHm(B298.15 K) 298.15 K


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rH1

rH2

rHm

rH1= - (fHi)rH2= (fHi)

rHm= (fHi)- (fHi)


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aA + dD = gG + hH

rHm(298) = gfHm(G) + hfHm(H)

- afHm(A) - dfHm(D)

T

rHm(T)rHm(298) =rHm


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5 CaCO3(s) = CaO(s) + CO2 (g)


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CaCO3(s) = CaO(s) + CO2 (g)

fHm/kJmol-1 -1206.9 -635.6 -393.5

rHm= [(-635.6) + (-393.5) (-1206.9)]

= 177 kJmol-1


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63C2H2(g) = C6H6(g)


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  • 3C2H2(g) = C6H6(g)

    fHm/kJmol-1 227 83

    rHm= 83 3227 = 598 kJmol-1


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  • fHm(H+,aq) = 0

    HCl(g) = H+(aq) + Cl-(aq)

    rHm= -74.7 kJ.mol-1

    rHm= fHm(H+,aq) + fHm(Cl- , aq) -fHm(HCl)

    = fHm(Cl-,aq) - fHm(HCl)

    fHm(Cl-aq) = rHm + fHm(HCl)

    = -74.7 + (-92.31)

    = -167.01 kJ.mol-1


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Zn(s) + Cu2+(aq) = Zn2+(aq) + Cu(s)

rHm = fHm(Zn2+,aq) - fHm(Cu2+,aq)


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