Stoichiometry and Mole Calculations
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Questions and Answers

In the reaction of ammonia (NH3) with carbon dioxide (CO2) to form urea [(NH2)2CO], what is the limiting reagent when 637.2 g of NH3 react with 1142 g of CO2?

  • Ammonia (NH3) (correct)
  • Carbon dioxide (CO2)
  • Urea [(NH2)2CO]
  • Neither, they react completely

    • If 3.4 moles of sulfur dioxide (SO2) react with excess oxygen (O2), how many moles of sulfur trioxide (SO3) will form?

  • 13.6 moles
  • 1.7 moles
  • 3.4 moles (correct)
  • 6.8 moles

    • What is the theoretical yield of titanium (Ti) in grams when 3.54 x 10^7 g of titanium(IV) chloride (TiCl4) react with 1.13 x 10^7 g of magnesium (Mg)?

  • 7.91 x 10^6 g (correct)
  • 3.54 x 10^7 g
  • 1.13 x 10^7 g
  • 1.58 x 10^7 g

    • In the reaction of titanium(IV) chloride (TiCl4) with magnesium (Mg) to form titanium (Ti), if 7.91 x 10^6 g of Ti are actually obtained, what is the percent yield of the reaction?

    <p>22.3% (D)</p> Signup and view all the answers

    What is the limiting reagent in the reaction of lithium (Li) with nitrogen (N2) to form lithium nitride (Li3N) when 2 moles of Li are reacted with 1 mole of N2?

    <p>Nitrogen (N2) (A)</p> Signup and view all the answers

    What is the theoretical yield, in grams, of urea [(NH2)2CO] when 637.2 g of ammonia (NH3) react completely with 1142 g of carbon dioxide (CO2)?

    <p>1364 g (B)</p> Signup and view all the answers

    When calculating the theoretical yield of a product, what information is necessary?

    <p>All of the above (D)</p> Signup and view all the answers

    Titanium is a strong, lightweight, corrosion-resistant metal used in various applications. What is its main source?

    <p>Titanium(IV) chloride (TiCl4) (B)</p> Signup and view all the answers

    What is the difference between the actual yield and theoretical yield in a chemical reaction?

    <p>Actual yield is always less than the theoretical yield (D)</p> Signup and view all the answers

    What is the purpose of calculating the percent yield of a reaction?

    <p>To determine the efficiency of the reaction (D)</p> Signup and view all the answers

    What is the molar mass of sulfur dioxide (SO2)?

    <p>64.06 g/mol (B)</p> Signup and view all the answers

    How many moles of zinc (Zn) are there in 23.3 g of Zn?

    <p>0.355 mol (D)</p> Signup and view all the answers

    What is the mass (in grams) of one silver (Ag) atom?

    <p>1.07 x 10^-22 g (A)</p> Signup and view all the answers

    What is the molecular mass of caffeine (C8H10N4O2)?

    <p>194.19 g/mol (D)</p> Signup and view all the answers

    How many moles of CH4 are present in 6.07 g of CH4?

    <p>0.378 mol (B)</p> Signup and view all the answers

    What is the percent by mass of sulfur in sulfur dioxide (SO2)?

    <p>50.05% (B)</p> Signup and view all the answers

    What is the name given to the quantitative study of reactants and products in a chemical reaction?

    <p>Stoichiometry (A)</p> Signup and view all the answers

    What is the meaning of the term "mole"?

    <p>A unit of measurement for the amount of a substance (D)</p> Signup and view all the answers

    What is Avogadro's number?

    <p>The number of atoms in one mole of a substance (D)</p> Signup and view all the answers

    What is the relationship between the molar mass of a substance and its molecular mass?

    <p>The molar mass is numerically equal to the molecular mass, but the units are different. (B)</p> Signup and view all the answers

    What is the mass of carbon dioxide (CO2) produced when 856 g of glucose (C6H12O6) is degraded?

    <p>2304 g (D)</p> Signup and view all the answers

    What is the percent composition by mass of hydrogen (H) in phosphoric acid (H3PO4)?

    <p>3.09% (B)</p> Signup and view all the answers

    If 2.00 moles of oxygen (O2) are used in the reaction between ammonia (NH3) and oxygen to produce nitrogen monoxide (NO) and water (H2O), how many moles of water are produced?

    <p>4.00 moles (A)</p> Signup and view all the answers

    How many grams of lithium (Li) are needed to produce 9.89 g of hydrogen gas (H2) when lithium reacts with water?

    <p>69.3 g (C)</p> Signup and view all the answers

    What is the limiting reagent in the reaction between 2.2 mol of ammonia (NH3) and excess oxygen to produce nitrogen monoxide (NO) and water (H2O)?

    <p>Ammonia (NH3) (D)</p> Signup and view all the answers

    Which of the following statements about the reaction between ammonia (NH3) and oxygen to produce nitrogen monoxide (NO) and water (H2O) is TRUE?

    <p>The reaction produces 6 moles of water (H2O) for every 4 moles of ammonia (NH3) consumed. (A)</p> Signup and view all the answers

    In the reaction between lithium (Li) and water (H2O), which of the following is NOT produced?

    <p>Lithium oxide (Li2O) (A)</p> Signup and view all the answers

    What is the molar mass of glucose (C6H12O6)?

    <p>180.16 g/mol (A)</p> Signup and view all the answers

    What is the mass of 2.2 mol of ammonia (NH3)?

    <p>37.47 g (C)</p> Signup and view all the answers

    Which of the following is NOT a common use of phosphoric acid (H3PO4)?

    <p>Antibiotics (B)</p> Signup and view all the answers

    Flashcards

    Stoichiometry

    The quantitative study of reactants and products in a chemical reaction.

    Mole (mol)

    The amount of a substance containing as many elementary entities as atoms in 12 g of carbon-12.

    Molar Mass

    The mass of 1 mole of units of a substance, expressed in grams per mole (g/mol).

    Avogadro’s Number

    The number of particles in one mole of a substance, approximately 6.022 x 10²³.

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    Molecular Mass

    The sum of atomic masses in a molecule, measured in atomic mass units (amu).

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    Percent Composition

    The percent by mass of each element in a compound.

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    Conversion Factor

    A ratio that expresses how many of one unit are equal to another unit.

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    Atomic Mass

    The mass of an atom expressed in atomic mass units (amu).

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    Example of Mole Calculation

    To find moles, divide mass by molar mass.

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    Molecular Mass of SO2

    Sum of atomic masses of sulfur and oxygen in sulfur dioxide.

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    Molar Mass of H3PO4

    The mass of one mole of phosphoric acid (H3PO4) is 97.99 g.

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    Balanced Equation

    An equation where the number of atoms for each element is equal on both sides.

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    Mole Ratio

    A ratio derived from the coefficients of a balanced equation.

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    Limiting Reagent

    The reactant that is consumed first, limiting the amount of product formed.

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    Excess Reagents

    Reactants present in quantities greater than necessary for the reaction.

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    Degradation of Glucose

    The process of breaking down glucose to produce energy.

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    Grams to Moles Conversion

    Calculating moles from grams using molar mass.

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    Water Production in Reactions

    The formation of water as a product in chemical reactions.

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    Theoretical Yield

    The maximum amount of product predicted by stoichiometry from a reaction.

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    Actual Yield

    The amount of product actually obtained from a reaction.

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    Percent Yield

    The ratio of actual yield to theoretical yield expressed as a percentage.

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    Reaction Yield

    The amount of product generated by a reaction; often compared to expected yields.

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    Balancing Chemical Equations

    The process of ensuring that the number of atoms of each element is the same on both sides of a reaction.

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    Combustion Reaction

    A chemical reaction that occurs when a substance combines with oxygen, releasing energy in the form of light or heat.

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    Study Notes

    Stoichiometry

    • Stoichiometry is the quantitative study of reactants and products in a chemical reaction.
    • "Stochio" means element in Greek, and "metry" means measurement.
    • Stoichiometric coefficients in a chemical equation represent the number of moles of each substance.

    Mole Method

    • Stoichiometric coefficients in a chemical equation represent the number of moles of each substance.
    • One mole of any pure substance contains Avogadro's number of particles.
    • Avogadro's number (NA) = 6.0221415 x 1023

    Mole

    • A mole (mol) is the amount of a substance that contains as many elementary entities (atoms, molecules, or other particles) as there are atoms in 12 grams of carbon-12.
    • Molar mass is the mass (in grams or kilograms) of one mole of a substance.
    • Atomic mass (or atomic weight) is the mass of an atom, expressed in atomic mass units (amu).

    Example Calculation

    • Calculate the moles of Zn in 23.3 g of Zn:
    • Molar mass of Zn = 65.39 g/mol
    • Moles of Zn = 23.3 g / 65.39 g/mol = 0.356 mol

    Example Calculation 2

    • Calculate the number of atoms in 16.3 g of S:
    • Molar mass of S = 32.07 g/mol
    • Moles of S = 16.3 g / 32.07 g/mol = 0.508 mol
    • Number of atoms = 0.508 mol x 6.022 x 1023 atoms/mol = 3.06 x 1023 atoms

    Molecular Mass

    • Molecular mass is the sum of the atomic masses of all atoms in a molecule.
    • Calculate the molecular mass of SO2:
    • Molecular mass of SO2 = (32.07 amu) + 2(16.00 amu) = 64.07 amu
    • Calculate the molar mass using the molecular mass:
    • The molar mass of a compound is numerically equal to its molecular mass in amu. For example, the molar mass of SO2 is 64.07 g/mol.

    Molar Mass Calculation Example

    • Calculate the moles of CH4 in 6.07 g of CH4:
    • Molar mass of CH4 = 16.04 g/mol
    • Moles of CH4 = 6.07g / 16.04 g/mol = 0.378 mol

    Percent Composition

    • The percentage composition of an element in a compound is the mass percent of that element in the compound.
    • Calculate the percent composition of H in H3PO4:
    • Percent composition of H = (3 x 1.008 g/mol) / (97.99 g/mol) x 100% = 3.09%

    Stoichiometry of Amounts of Reactants and Products

    • Coefficients in a balanced chemical reaction represent the mole ratio of reactants and products.
    • Example:
    • In the reaction 4NH3 + 5O2 → 6H2O + 4NO, the mole ratio between NH3 and H2O is 4:6, which can simplify to 2:3 .

    Limiting Reactants

    • Limiting reagent: The reactant that is completely consumed in a chemical reaction. Determines the maximum amount of product.
    • Excess reagents: The reactants that are present in greater quantity than is required to react completely with the limiting reagent.

    Sample Problem Calculation (Limiting Reagent)

    • Given 8 moles of NO and 7 moles of O2, determine the limiting reagent for the reaction 2NO + O2 → 2NO2
    • Calculate moles of NO2 from NO: 8mol NO x (2 mol NO2/2 mol NO) = 8 mol NO2
    • Calculate moles of NO2 from O2: 7 mol O2 x (2 mol NO2/1 mol O2) = 14 mol NO2
    • The smaller value is 8, meaning NO is the limiting reagent.

    Reaction Yield

    • Theoretical yield: The maximum amount of product that can be produced given a complete reaction of the limiting reagent.
    • Actual yield: The amount of product that is actually isolated or obtained from a reaction often less than the theoretical yield.

    Percent Yield

    • % yield = (actual yield / theoretical yield) x 100%

    Stoichiometry Problems Examples

    • The given examples include problems involving calculating moles, grams, substances present in a chemical reaction, using different amounts of reagents present, and calculating the percent yield.

    Additional Concepts

    • Stoichiometry calculations often involve converting between moles, mass, and number of particles.

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    Stoichiometry-STEM PDF

    Description

    Explore the fundamentals of stoichiometry and the mole method in this quiz. Understand the relationship between reactants and products in a chemical equation, and learn how to perform calculations using molar mass and Avogadro's number. Test your knowledge with practical examples to solidify your understanding.

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