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    CEM1008F - 4. Molecules, Moles and Chemical Equations Stochiometry 2022 Presentation Part 2 Notes

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    This document provides an overview of stoichiometry and its applications to chemistry. It discusses [1] mole-mass relationships in chemical reactions, [2] writing and balancing chemical equations, and [3] using balanced equations to calculate amounts of reactants and products. Limiting reactants and percent yields are also covered. Finally, the document discusses stoichiometry as it applies to solutions, including calculating molarity and the amounts of solutes and products in reactions in solution.

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    CEM1008F - 4. Molecules, Moles and Chemical Equations Stochiometry 2022 Presentation Part 2 Notes

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    This document provides an overview of stoichiometry and its applications to chemistry. It discusses [1] mole-mass relationships in chemical reactions, [2] writing and balancing chemical equations, and [3] using balanced equations to calculate amounts of reactants and products. Limiting reactants and percent yields are also covered. Finally, the document discusses stoichiometry as it applies to solutions, including calculating molarity and the amounts of solutes and products in reactions in solution.

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    This document provides an overview of stoichiometry and its applications to chemistry. It discusses [1] mole-mass relationships in chemical reactions, [2] writing and balancing chemical equations, and [3] using balanced equations to calculate amounts of reactants and products. Limiting reactants and percent yields are also covered. Finally, the document discusses stoichiometry as it applies to solutions, including calculating molarity and the amounts of solutes and products in reactions in solution.

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    23 views24 pages

    CEM1008F - 4. Molecules, Moles and Chemical Equations Stochiometry 2022 Presentation Part 2 Notes

    Uploaded by

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    This document provides an overview of stoichiometry and its applications to chemistry. It discusses [1] mole-mass relationships in chemical reactions, [2] writing and balancing chemical equations, and [3] using balanced equations to calculate amounts of reactants and products. Limiting reactants and percent yields are also covered. Finally, the document discusses stoichiometry as it applies to solutions, including calculating molarity and the amounts of solutes and products in reactions in solution.

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    of 24

    CEM1008F

    CHEMISTRY FOR ENGINEERS

    Lecture Notes Part 2:


    Molecules, Moles and Chemical Equations
    Stoichiometry
    Mole - Mass Relationships in Chemical Systems

    3.1 The Mole

    3.2 Determining the Formula of an Unknown Compound

    3.3 Writing and Balancing Chemical Equations

    3.4 Calculating the Amounts of Reactant and Product

    3.5 Fundamentals of Solution Stoichiometry

    2
    Writing and Balancing Chemical
    Equations

    · A chemical equation is a statement in formulae


    that expresses the identities and quantities of the
    substances involved in a chemical or physical
    change
    · Left side = reactants – before the change
    · Right side = products – substances present after
    reaction
    · Balanced reaction = the same number of each
    type of atom must appear on both sides of the
    equation
    · Balancing (stoichiometric) coefficients
    3
    Balancing Chemical Equations

    • All atoms on the left must be found on the right.


    • Obey Law of Conservation of Mass
    • Subscripts of a compound are fixed; they cannot be
    changed, as we would change the identity of the
    compound.
    • Use coefficients – placed before a chemical formula
    in an equation.
    • Coefficients should be the smallest whole numbers
    possible.
    • Coefficient multiplies every number in the formula.
    4
    Using Chemical Equations in
    Calculations
    • If you know the number of moles of one substance, the balanced
    equation tells you the number of moles of all the others in the
    reaction
    • The number of moles of one substance is stoichiometrically
    equivalent to the number of moles of any substance
    • Limiting Reactant Calculations :
    – Also known as the limiting reagent
    – Reactant that yields the lower amount of product
    • Theoretical Yield and Percentage Yield :
    – Theoretical yield = amount indicated by the stoichiometrically
    equivalent molar ratio in the balanced equation
    – Side reactions occur
    – % yield = (actual yield / theoretical yield) x 100

    5
    Using Chemical Equations in
    Calculations
    • N2 (g) + 3 H2 (g) → 2 NH3 (g)

    1 mol N2 produces 2 mol NH3

    3 mol H2 produces 2 mol NH3

    1 mol N2 reacts with 3 mol H2


    6
    Using Chemical Equations in
    Calculations
    • When aluminium metal reacts with HCl,
    aluminium chloride and hydrogen gas are
    produced.

    If 4.288 g of Al undergo this reaction with HCl,


    how many grams of hydrogen gas should be
    produced?

    7
    Summary of the Mass-Mole-Number
    Relationships in a Chemical Reaction

    8
    Calculating Amounts of Reactant and Product in
    Reactions Involving a Limiting Reactant
    PROBLEM: A fuel mixture used in the early days of rocketry is composed of
    two liquids, hydrazine (N2H4) and dinitrogen tetroxide (N2O4),
    which ignite on contact to form nitrogen gas and water vapour.
    How many grams of nitrogen gas form when 1.00x102 g of N2H4
    and 2.00x102 g of N2O4 are mixed?

    9
    An Ice Cream Sundae Analogy for Limiting Reactions

    Figure 3.10

    10
    Calculating Amounts of Reactant and Product in
    Reactions Involving a Limiting Reactant
    continued

    11
    Calculating Percent Yield

    PROBLEM: Silicon carbide (SiC) is an important ceramic material that is


    made by allowing sand (silicon dioxide, SiO2) to react with
    powdered carbon at high temperature. Carbon monoxide is also
    formed. When 100.0 kg of sand are processed, 51.4 kg of SiC
    are recovered. What is the percent yield of SiC in this process?

    12
    Solution Stoichiometry

    • Solute- smaller amount of one substance, dissolved


    in a larger amount of another substance, the solvent
    • Concentration of a solution is expressed as the
    amount of solute dissolved in a given amount of
    solution
    • Molarity(M) = mole of solute(mol) / volume of solution(L)
    • Mole-Mass-Number Conversions Involving Solutions
    • Preparing and diluting molar solutions

    13
    Calculating the Molarity of a Solution

    PROBLEM: Hydrobromic acid (HBr) is a solution of hydrogen bromide gas in


    water. Calculate the molarity of hydrobromic acid solution if 455 mL
    contains 1.80 mol of hydrogen bromide.

    14
    Calculating Mass of Solute in a Given
    Volume of Solution
    PROBLEM: How many grams of solute are in 1.75 L of 0.460 M sodium
    hydrogen phosphate?

    15
    Converting a Concentrated Solution to a Dilute Solution

    16
    Preparing a Dilute Solution from a
    Concentrated Solution
    PROBLEM: “Isotonic saline” is a 0.15 M aqueous solution of NaCl that
    simulates the total concentration of ions found in many cellular
    fluids. Its uses range from a cleaning rinse for contact lenses to
    a washing medium for red blood cells. How would you prepare
    0.80 L of isotonic saline from a 6.0 M stock solution?

    17
    18
    Calculating Amounts of Reactants and
    Products for a Reaction in Solution

    PROBLEM: Specialized cells in the stomach release HCl to aid digestion. If


    they release too much, the excess can be neutralized with
    antacids. A common antacid contains magnesium hydroxide,
    which reacts with the acid to form water and magnesium
    chloride solution. As a government chemist testing commercial
    antacids, you use 0.10 M HCl to simulate the acid concentration
    in the stomach. How many liters of “stomach acid” react with a
    tablet containing 0.10 g of magnesium hydroxide?

    19
    Calculating Amounts of Reactants and
    Products for a Reaction in Solution
    continued

    20
    Solving Limiting-Reactant Problems
    for Reactions in Solution

    PROBLEM: Mercury and its compounds have many uses, from filling teeth
    (as an alloy with silver, copper, and tin) to the industrial
    production of chlorine. Because of their toxicity, however,
    soluble mercury compounds, such mercury(II) nitrate, must be
    removed from industrial wastewater. One removal method
    reacts the wastewater with sodium sulfide solution to produce
    solid mercury(II) sulfide and sodium nitrate solution. In a
    laboratory simulation, 0.050 L of 0.010 M mercury(II) nitrate
    reacts with 0.020 L of 0.10 M sodium sulfide. How many grams
    of mercury(II) sulfide form?

    21
    Solving Limiting-Reactant Problems
    for Reactions in Solution
    continued

    22
    Laboratory Preparation of Molar Solutions

    23
    24

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