modul persamaan laju reaksi

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  • 1. Teacher Training and Educational Studies Sebelas Maret University M. Masykuri_Physical Chemistry IV Sep, 2010 01/30/15 1 Dr. M. Masykuri, M.Si. Chemical Education Study Program Teacher Training and Educational Studies Sebelas Maret University (UNS) Website: http://masykuri.staf.fkip.uns.ac.id, email: [email protected] Solo, Sep 2010 Kimia Fisika IV

2. Teacher Training and Educational Studies Sebelas Maret University M. Masykuri_Physical Chemistry IV Sep, 2010 Rate of Reaction Consider a chemical reaction having the overall stoichiometry: aA + bB cC + dD The Rate of Reaction is defined as Experimentally we find that k = rate coefficient Ci = Concentration of Reactant i or [i] i = Order of reaction with respect to reactant i 3. Teacher Training and Educational Studies Sebelas Maret University M. Masykuri_Physical Chemistry IV Sep, 2010 Macam Metode Metode Penentuan Tetapan Laju: Metode relaksasi, metode analisis guegenheim 4. Teacher Training and Educational Studies Sebelas Maret University M. Masykuri_Physical Chemistry IV Sep, 2010 Metode Diferensial Data dikumpulkan sebagai laju perubahan konsentrasi/waktu terhadap konsentrasi reaktan. Contoh dasar persamaan bagi reaksi dengan 2 reaktan: aA + bB produk qp BAk dt Ad r ][][ ][ == ]ln[]ln[ln ][ lnln BqApk dt Ad r ++= = Dibuat kurva ln r terhadap ln [A] atau ln [B] 5. Teacher Training and Educational Studies Sebelas Maret University M. Masykuri_Physical Chemistry IV Sep, 2010 Metode Diferensial ]ln[]ln[ln ][ lnln BqApk dt Ad r ++= = Kurva ln r terhadap ln [A] ]ln['lnln Apkr += Orde reaksi terhadap A = p, diperoleh dari slope = tg Tetapan laju k, diperoleh dari intersep grafik Orde reaksi terhadap A = p, diperoleh dari slope = tg Tetapan laju k, diperoleh dari intersep grafik Slope = tg = p ]ln[ln'ln BqkkIntersep +== 6. Teacher Training and Educational Studies Sebelas Maret University M. Masykuri_Physical Chemistry IV Sep, 2010 Metode Diferensial Data konsentrasi zat A pada reaksi, yang dikatalisis suatu katalis C sebagai fungsi waktu diketahui sbb: A produk Contoh: t (menit) A (M) t (menit) A (M) 0 0,800 8 0,382 2 0,647 10 0,329 4 0,534 12 0,286 6 0,448 14 0,252 a. Tentukan orde reaksi terhadap A sampai kelipatan terdekat b. Tentukan harga tetapan laju reaksi k dengan satuannya yang tepat 7. Teacher Training and Educational Studies Sebelas Maret University M. Masykuri_Physical Chemistry IV Sep, 2010 Metode Integral Bersifat trial and error (empiris), yaitu dengan memasukkan data pada persamaan laju bentuk integral. Jika harga k relatif tetap (konstan), maka orde reaksinya sesuai. Penentuan empiris orde reaksi terhadap reaktan: Orde nol Orde pertama Orde kedua tipe I Orde kedua tipe II Prde ketiga 8. Teacher Training and Educational Studies Sebelas Maret University M. Masykuri_Physical Chemistry IV Sep, 2010 Metode Integral The rate of the reaction is independent of the concentration of the reacting substance Zero Order Reactions A products = = = dtkAd k dt Ad k dt Ad A A ][ ][ 0 ][ ][ ][ [A]t - [A]0 = - kt The reaction half-time t1/2 is the time required for the concentration to decrease to one-half of its initial value. 9. Teacher Training and Educational Studies Sebelas Maret University M. Masykuri_Physical Chemistry IV Sep, 2010 Metode Integral Zero Order Reactions Grafik [A] versus t, Persamaan grafik, Slope = - k Intersep = [A]0 Waktu paruh, 10. Teacher Training and Educational Studies Sebelas Maret University M. Masykuri_Physical Chemistry IV Sep, 2010 Metode Integral First Order Reactions The rate of the reaction is proportional to the first power of the concentration of the reacting substance (order = 1) A products = = = dtk A Ad kdt A Ad Ak dt Ad A A ][ ][ 0 ][ ][ ][ ][ ][ ][ Examples: decay of radioactive nuclei fluorescence decay of electronically excited molecules isomerization of cyclobutene to butadiene milk turns sour when left out overnight 11. Teacher Training and Educational Studies Sebelas Maret University M. Masykuri_Physical Chemistry IV Sep, 2010 Metode Integral First Order Reactions Grafik ln [A] versus t, Persamaan grafik, Buktikan bahwa, 12. Teacher Training and Educational Studies Sebelas Maret University M. Masykuri_Physical Chemistry IV Sep, 2010 Metode Integral Second Order Reactions The rate of the reaction is proportional to the second power of the concentration of one reactant or to the first power of the concentrations of two reactants (order = 2) a) Second order in one componenta) Second order in one component A products b) First order in each of two componentsb) First order in each of two components A +B products 13. Teacher Training and Educational Studies Sebelas Maret University M. Masykuri_Physical Chemistry IV Sep, 2010 Metode Integral Second Order Reactions a) Second order in one componenta) Second order in one component A products 14. Teacher Training and Educational Studies Sebelas Maret University M. Masykuri_Physical Chemistry IV Sep, 2010 b) First order in each of two componentsb) First order in each of two components Metode Integral Second Order Reactions A +B products Special cases: i) [A]o = [B]o ii) [B]o