Chapter 3_ Mole Concept and Stoichiometry.pdf -...

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Chapter 3. Mole Concept and Stoichiometry After studying this topic you should be able to: Define and express the concept of mole and its application Define and calculate relative molecular mass and formula mass Calculate moles, mass and number of particles Define and determine empirical and molecular formulas Identify the type of reaction Write balanced chemical equations by inspection method Calculate the amount of compounds based on chemical equation Perform stoichiometric calculations using mole concept Define limiting reactant and percentage yield Calculate theoretical yield, actual yield and percentage CHM101/Chapter 3 1
The Periodic Table CHM101/Chapter 3 2
Mole , symbol mol The SI base unit of measurement for the amount of substance A mole (one mole), 1 mol The quantity of any substance that contains same No. of entities (particles such as atoms, molecules, ions, electrons or formula units) as the No. of atoms present in exactly 12 g of carbon-12 isotope The No. corresponds to the Avogadro constant (N A or L) N A = 6.022 x 10 23 mol -1 (more exactly 6.02214129 x 10 23 #) Examples 1 mol C-12 contains 6.022 x 10 23 carbon-12 atoms (element) 1 mol H O contains 6 022 x 10 23 water molecules The Mole Concept CHM101/Chapter 3 3
Molar Mass Molar mass (M m or M r ) The mass of 1 mole of a substance (element or compound) Units is g/mol (in grams per mole ) Numerically equal to molecular weight or formula weight in amu (u) e.g. Molecular weight of glucose (C 6 H 12 O 6 ) =180 amu (u) Molar mass of glucose (C 6 H 12 O 6 ) =180 g/mol Molar mass of a substance (cf. atomic mass for 1 mole of atoms ) Molecular mass for 1 mole of molecules Formula mass for 1 mole of molecules or ionic compound Calculated as the sum of the atomic masses of all the atoms present in one formula unit of the substance l h CHM101/Chapter 3 4
Moles, mass and molar mass can be related by formula Moles = mass / molar mass Molar mass = mass / moles No. of atoms , molar mass, mass and moles of an element is related as No. of particles = No. of mol x Avogadro constant No. of particles (atoms) = Can be applied for molecules, ions or formula units e.g. calculate the No. of hydrogen atoms in 20 g of C 2 H 5 OH Molar Mass – Mass – Mole Relationship CHM101/Chapter 3 5
Relative Molecular Mass or Molecular Weight Relative molecular mass (M r ) of a molecular substance The sum of relative atomic masses (A r ) of all atoms in the molecular formula (covalent compounds made up of molecules) Examples: ethanol, benzene, S 8 , caffeine (C 8 H 10 N 4 O 2 ), etc. Relative formula mass of a compound ( ionic or molecular substance ) The sum of relative atomic masses (A r ) of all the atoms in the chemical formula of the compound Used for ionic compounds and molecular compounds No units, but for molecules in amu (u) and for 1 mole, in grams per mol CHM101/Chapter 3 6
What is the mass of a HCl molecule in grams?
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