Factors Affecting the Rate of Chemical Reaction PDF
Document Details
Uploaded by BonnyCornett
Ahmed Zewail Language School
Tags
Summary
This document provides an overview of factors affecting the rate of chemical reactions. It discusses the nature of reactants, including ionic and covalent compounds, and how surface area and concentration influence the reaction rate. Equilibrium concepts and the equilibrium constant are also introduced.
Full Transcript
# Factors Affecting the Rate of Chemical Reaction ## Factors Affecting the Rate of Chemical Reaction - Nature of reactants - Type of Bonding in the reactants - **Ionic Compounds react fast** - The reaction takes place between ions (they are ionized). - The ions...
# Factors Affecting the Rate of Chemical Reaction ## Factors Affecting the Rate of Chemical Reaction - Nature of reactants - Type of Bonding in the reactants - **Ionic Compounds react fast** - The reaction takes place between ions (they are ionized). - The ions react with each other instantly as soon as mixed. - **Covalent Compounds react slowly** - The reaction takes place between molecules (not ionized). - An amount of energy is consumed to break the covalent bond. - So time is consumed. - Surface Area - As the surface area increases, the chance of more collisions increases, so the rate of reaction increases. - Powder form is better than block form. ## Concentration of Reactants - **Collision Theory:** To have a chemical reaction, the molecules of the reactants must collide with each other. - As the concentration increases, the rate of collision between the reacting molecules increases, so the rate of reaction increases. ## Law of Mass Action - At a constant temperature, the rate of a chemical reaction is directly proportional to the product of the concentrations of the reactants, each raised to the power of its stoichiometric coefficient. ## Equilibrium Constant - FeCl<sub>3</sub> + 3NH<sub>4</sub>SCN ⇌ 3NH<sub>4</sub>Cl + Fe(SCN)<sub>3</sub> - Pale yellow (Color of the reactants) - Iron III thiocyanate (Bloodred) - **Rate Constant of Forward Reaction:** - r<sub>1</sub> = K<sub>1</sub>[FeCl<sub>3</sub>][NH<sub>4</sub>SCN]<sup>3</sup> - **Rate Constant of Reverse Reaction:** - r<sub>2</sub>=K<sub>2</sub> [NH<sub>4</sub>Cl]<sup>3</sup>[Fe(SCN)<sub>3</sub>] - **At Equilibrium, r<sub>1</sub>=r<sub>2</sub>** - K<sub>1</sub>[FeCl<sub>3</sub>][NH<sub>4</sub>SCN]<sup>3</sup> = K<sub>2</sub>[NH<sub>4</sub>Cl]<sup>3</sup>[Fe(SCN)<sub>3</sub>] - **Equilibrium Constant:** - K<sub>c</sub>= (Conc. of products)/(Conc. of reactants) - **K<sub>c</sub> = [NH<sub>4</sub>Cl]<sup>3</sup>[Fe(SCN)<sub>3</sub>] / [FeCl<sub>3</sub>][NH<sub>4</sub>SCN]<sup>3</sup>** - **K<sub>c</sub> = [NH<sub>3</sub>]<sup>2</sup>/[N<sub>2</sub>][H<sub>2</sub>]<sup>3</sup>** ### K<sub>c</sub> value: - **Less than 1:** Conc. of reactants > Conc. of products. The reaction directs backward. - **Higher than 1:** Conc. of products > Conc. of reactants. The forward reaction is the predominate. - **Reversible Reaction:** The reaction directs to its completion. - **Complete Reaction:** Preparation of hydrogen halides from its constituent elements - H<sub>2</sub> + Cl<sub>2</sub> ⇌ 2HCl - H<sub>2</sub> + I<sub>2</sub> ⇌ 2HI ### Solids & Liquids - **Solids:** Can't appear in the equilibrium constant expression. - **Liquids:** Their concentration remains constant, whatever the quantity. - Ag(s) + 2HNO<sub>3</sub>(aq) ⇌ 2AgNO<sub>3</sub>(aq) + H<sub>2</sub>(g) - K<sub>c</sub> = [AgNO<sub>3</sub>]<sup>2</sup>/[HNO<sub>3</sub>]<sup>2</sup> ### Equilibrium Constant & Stoichiometry - A + B ⇌ AB K<sub>c</sub> = K - 2A + B ⇌ 2AB K<sub>c</sub> = 2 - 1/2A + 1/2B ⇌ 1/2AB K<sub>c</sub> = √x - AB ⇌ A + B K<sub>c</sub> = 1/x - 2AB ⇌ 2A + 2B K<sub>c</sub> = 1/x<sup>2</sup> - 1/2AB ⇌ 1/2A + 1/2B K<sub>c</sub> = √(1/x) = 1/√x
