[H2 CHEM] Chapter 6 - The Mole Concept and Stoichiometry

ELAINE PEH (COPYRIGHTED) © Chapter 6 The Mole Concept & Stoichiometry

CHAPTER ANALYSIS FOCUS EXAM WEIGHTAGE ELAINE PEH (COPYRIGHTED) ©

Atoms & Other Particles Atomic Mass & Molecular Mass Mole & Related Formula Empirical Formula & Molecular Formula KEY CONCEPT ELAINE PEH (COPYRIGHTED) ©

Balancing Chemical Equation & Stoichiometric Mole Ratio Concentration of Solution Titrations (Volumetric Analysis) Practical KEY CONCEPT ELAINE PEH (COPYRIGHTED) ©

ATOMS The smallest particle of an element. MOLECULES A group of atoms covalently bonded together in an element or a compound. ISOTOPES Atoms of the same element with the same number of protons/electrons but different number of neutrons ELAINE PEH (COPYRIGHTED) © Atoms & Other Particles

Atomic Mass & Molecular Mass PROTON NUMBER VS NUCLEON NUMBER Refer to the number of protons/electrons in an atom. Refer to the total number of protons and neutrons in an atom. RELATIVE ATOMIC MASS, Ar Average mass of one atom of the element as compared to 1 12 of the mass of one atom of carbon-12. RELATIVE ISOTOPIC MASS, Ar Mass of one atom of an isotope of an element as compared to 1 12 of the mass of one atom of carbon-12. RELATIVE MOLECULAR MASS, Mr Average mass of one molecule of the substances as compared to 1 12 of the mass of one atom of carbon-12. Average Isotopic = Mass Σ [(relative isotopic mass)(% abundance)] ELAINE PEH (COPYRIGHTED) ©

MOLES One mole contains exactly 6.02 x 1023 (Avogadro constant) elementary particles. MOLAR MASS It is numerically equal to Ar or Mr with units of g mol-1. MOLAR VOLUME The volume occupied by one mole of gas with units of dm3 mol-1. (Commonly used values = 24.0 dm3mol-1& 22.7 dm3mol-1) ELAINE PEH (COPYRIGHTED) © Mole & Related Formula

EMPIRICAL FORMULA Simplest formula which the ratio of atoms of the different elements in the compound. Determination of Empirical Formula Step 1: Write down the mass ratio of the elements involved Step 2: Convert the mass ratio into mole ratio Step 3: Determine the smallest whole number values for the mole ratio obtained. MOLECULAR FORMULA Actual formula which shows the actual number of atoms of each element in one molecule of the compound. Determination of Molecular Formula from Empirical Formula Step 1: Determine the empirical formula first Step 2: Determine n using the given Mr* *Mr of molecular formula = (Mr of empirical formula)n ELAINE PEH (COPYRIGHTED) © Empirical Formula & Molecular Formula

MOLECUALR FORMULA COMBUSTION DATA OF HYDROCARBON 1) By the use of Mass Ratio - All the weight from a pure element originated from the compound 2) By the use of Volume Ratio - Only for complete combustion ELAINE PEH (COPYRIGHTED) © Empirical Formula & Molecular Formula

CHEMICAL EQUATION A balanced chemical equation shows the mole ratio (stoichiometric ratio) of reactants and products. LIMITING REAGENT Sometimes reactants are not always added in stoichiometric amounts. When only one reactant is completely consumed at the end of the reaction, this reactant is the limiting reagent. THEORETICAL YIELD It is the yield calculated based on the chemical equation and the amount of reactants present. EXPERIMENTAL (ACTUAL) YIELD It is the actual yield calculated based on the amount of products actually obtained in a reaction. Note: The difference between theoretical yield and experimental yield is due to experimental losses ELAINE PEH (COPYRIGHTED) © Balancing Chemical Equation & Stoichiometric Mole Ratio