* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Lecture 14
Size-exclusion chromatography wikipedia , lookup
Multi-state modeling of biomolecules wikipedia , lookup
Biochemistry wikipedia , lookup
Chemical warfare wikipedia , lookup
Debye–Hückel equation wikipedia , lookup
Fluorochemical industry wikipedia , lookup
Fine chemical wikipedia , lookup
Electrochemistry wikipedia , lookup
Registration, Evaluation, Authorisation and Restriction of Chemicals wikipedia , lookup
Host–guest chemistry wikipedia , lookup
Determination of equilibrium constants wikipedia , lookup
California Green Chemistry Initiative wikipedia , lookup
Chemical equilibrium wikipedia , lookup
Click chemistry wikipedia , lookup
Process chemistry wikipedia , lookup
Safety data sheet wikipedia , lookup
Drug discovery wikipedia , lookup
History of chemistry wikipedia , lookup
Al-Shifa pharmaceutical factory wikipedia , lookup
Chemical weapon proliferation wikipedia , lookup
Chemical plant wikipedia , lookup
Chemical reaction wikipedia , lookup
Gas chromatography–mass spectrometry wikipedia , lookup
Chemical potential wikipedia , lookup
Organosulfur compounds wikipedia , lookup
Computational chemistry wikipedia , lookup
Chemical weapon wikipedia , lookup
Chemical industry wikipedia , lookup
Chemical Corps wikipedia , lookup
Rate equation wikipedia , lookup
History of molecular theory wikipedia , lookup
Physical organic chemistry wikipedia , lookup
Transition state theory wikipedia , lookup
Atomic theory wikipedia , lookup
Bioorthogonal chemistry wikipedia , lookup
VX (nerve agent) wikipedia , lookup
Chemistry 103 Lecture 14 Outline I. Empirical/Molecular Formulas II. Chemical Reactions - basic symbols - balancing - classification III. Stoichiometry Types of Formulas The molecular formula Is the true or actual number of the atoms in a molecule The empirical formula Is the simplest whole number ratio of the atoms (this is the formula for ionic compounds) H2O2 molecular formula HO empirical formula Empirical & Molecular Formulas Ionic Compounds - Only need Empirical formula. Molecules - Need information on both to determine exact make-up of your system Molecular Formula C 6H 6 Empirical Formula CH Relating Molecular and Empirical Formulas A molecular formula Is a multiple (or equal) of its empirical formula Has a molar mass that is the empirical mass multiplied by a whole number molar mass = a whole number empirical mass Is obtained by multiplying the empirical formula by a whole number Finding the Molecular Formula Determine the molecular formula of compound that has a molar mass of 78.11 g/mole and an empirical formula of CH. Molecular Formula A compound is 24.27% C, 4.07% H, and 71.65% Cl. The molar mass is known to be 99.0 g. What are the empirical and molecular formulas? Chemical Reactions Physical Change In a physical change, • The identity and composition of the substance do not change • The state can change or the material can be torn into smaller pieces Copyright © 2005 by Pearson Education, Inc. Publishing as Benjamin Cummings Chemical Change In a chemical change, • Reacting substances form new substances with different compositions and properties • A chemical reaction takes place Copyright © 2005 by Pearson Education, Inc. Publishing as Benjamin Cummings Chemical Reaction In a chemical reaction, Old bonds are broken and new bonds are formed Atoms in the reactants are rearranged to form one or more different substances Fe and O2 form rust (Fe2O3) Chemical Reaction In a chemical reaction, • A chemical change produces one or more new substances • There is a change in the composition of one or more substances Copyright © 2005 by Pearson Education, Inc. Publishing as Benjamin Cummings Evidence of a Chemical Reaction Changes that can be seen are evidence of a chemical reaction. Writing a Chemical Reaction Chemists use a shorthand approach when writing the specifics of a chemical reaction. This approach is called the chemical equation. Reactants -----> Products Chemical Equations A chemical equation, • Gives the chemical formulas of the reactants on the left of an arrow and the products on the right Reactants Product O2 (g) C(s) CO2 (g) Symbols Used in Equations Symbols used in chemical equations show: The states of the reactants The states of the products The reaction conditions Chemical Equations Are Balanced In a balanced chemical reaction, • Atoms are not gained or lost Chemical Equations Are Balanced In a balanced chemical reaction, • The number of reactant atoms are equal to the number of product atoms Chemical Equations •Chemical equations: symbolic descriptions of chemical reactions. •Two parts to an equation: •reactants and products H2 + O2 H2O A Chemical Equation must also be “balanced”. 2H2 + O2 --> 2H2O Balanced Chemical Equations Chemical Equations must be balanced There must be equal numbers of atoms of each element on both sides of the equation (both sides of the arrow) 1. Write the correct symbols and formulas for all of the reactants and products. 2. Count the number of each type of atom on BOTH sides of the equation. 3. Insert coefficients until there are the equal numbers of each kind of atom on both sides of the equation. Example - making ammonia Hydrogen gas and Nitrogen gas combine to make ammonia in the gaseous state. Example - making ammonia Hydrogen gas and Nitrogen gas combine to make ammonia in the gaseous state. H2(g) + N2(g) NH3 (g) Example - making ammonia Hydrogen gas and Nitrogen gas combine to make ammonia in the gaseous state. H2(g) + N2(g) NH3 (g) Example - making ammonia Hydrogen gas and Nitrogen gas combine to make ammonia in the gaseous state. H2(g) + N2(g) NH3 (g) Example - making ammonia Hydrogen gas and Nitrogen gas combine to make ammonia in the gaseous state. H2(g) + N2(g) 2 NH3 (g) Example - making ammonia Hydrogen gas and Nitrogen gas combine to make ammonia in the gaseous state. 3 H2(g) + N2(g) 2 NH3 (g) Example - making ammonia Hydrogen gas and Nitrogen gas combine to make ammonia in the gaseous state. BEFORE 3 H2(g) + N2(g) AFTER 2 NH3 (g) Balancing Equations Methane reacts with oxygen (combustion reaction) to form carbon dioxide and water. Write a properly balanced chemical equation The Numbers in Chemical Equations More Practice: Balancing Reactions C 2H 6 + O2 CO2 + H 2O C 3H 6 + O2 CO2 + H 2O NH3 + O2 NO + H 2O Stoichiometry Chemical Stoichiometry: using mass and quantity relationships among reactants and products in a chemical reaction to make predictions about how much product will be made. Quantities in a Chemical Reaction 4NH3(g) + 5O2(g) 4NO(g) + 6H2O(g) Four molecules NH3 react with five molecules O2 to produce four molecules NO and six molecules H2O Quantities in a Chemical Reaction 4NH3(g) + 5O2(g) 4NO(g) + 6H2O(g) Four molecules NH3 react with five molecules O2 to produce four molecules NO and six molecules H2O and Four mol NH3 react with five mol O2 to produce four mol NO and six mol H2O Moles in Equations We can read the equation in “moles” by placing the word “mole” or “mol” between each coefficient and formula. 4Fe(s) + 4 mol Fe + 3O2(g) 2Fe2O3(s) 3 mol O2 2 mol Fe2O3 Conservation of Mass The Law of Conservation of Mass indicates: • No change in total mass occurs in a reaction • Mass of products is equal to mass of reactants Law of Conservation of Mass In an ordinary chemical reaction, • Matter cannot be created or destroyed • The number of atoms of each element are equal • The mass of reactants equals the mass of products H2(g) + Cl2(g) 2HCl(g) 2 mol H, 2 mol Cl = 2(1.008) + 2(35.45) 72.92 g 2 mol H, 2 mol Cl = = 2(36.46) 72.92 g Conservation of Mass 2 mol Ag + 2 (107.9 g) + 1 mol S = 1 mol Ag2S 1(32.07 g) = 1 (247.9 g) = 247.9 g product 247.9 g reactants Writing Mole-Mole Factors A mole-mole factor is a ratio of the moles for two substances in an equation. 4Fe(s) + Fe and O2 Fe and Fe2O3 O2 and Fe2O3 3O2(g) 2Fe2O3(s) 4 mol Fe and 3 mol O2 4 mol Fe and 2 mol Fe2O3 3 mol O2 and 2 mol Fe2O3 3 mol O2 4 mol Fe 2 mol Fe2O3 4 mol Fe 2 mol Fe2O3 3 mol O2 Calculations with Mole Factors How many moles of Fe2O3 can form from 6.0 mol O2? 4Fe(s) + 3O2(g) Relationship: 2Fe2O3(s) 3 mol O2 = 2 mol Fe2O3 Write a mole-mole factor to determine the moles of Fe2O3. 6.0 mol O2 x 2 mol Fe2O3 = 4.0 mol Fe2O3 3 mol O2 Mole relations How many moles of Fe are needed to react with 12.0 mol O2? 4Fe(s) + 3O2(g) A) 3.00 mol Fe B) 9.00 mol Fe C) 16.0 mol Fe 2 Fe2O3(s)