Limiting Reactants in Chemical Reactions
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What is the role of the limiting reactant in a chemical reaction?

  • It determines the maximum amount of product formed. (correct)
  • It can be used to produce infinite amounts of product.
  • It is always present in larger quantities than other reactants.
  • It does not participate in the chemical reaction.

When calculating the excess reactant remaining after a reaction, which formula is used?

  • Excess moles = moles (reacted) - given moles
  • Excess mass = mass (reacted) + given mass
  • Excess moles = given moles + moles (reacted)
  • Excess mass = given mass - mass (reacted) (correct)

In the reaction 2Al + Fe2O3 → Al2O3 + 2Fe, if Aluminum (Al) is the limiting reactant, what can be determined about Iron(III) oxide (Fe2O3)?

  • It will be present in excess after the reaction. (correct)
  • It has no effect on the production of Al2O3.
  • It is the limiting reactant.
  • It will fully react with Aluminum to produce Al2O3.

What mass of Al2O3 is produced when 124 g of Al is reacted with 601 g of Fe2O3?

<p>Both options A and B. (D)</p> Signup and view all the answers

What is true about the excess reactant after a reaction has occurred?

<p>It is present in quantities greater than necessary. (B)</p> Signup and view all the answers

In the reaction between aluminum and iron(III) oxide, which reagent is identified as the limiting reagent?

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

What is the theoretical yield of aluminum oxide (Al2O3) produced when starting with 124 g of aluminum?

<p>234 g (A)</p> Signup and view all the answers

If 601 g of Fe2O3 is provided in the reaction with aluminum, what is the excess mass of Fe2O3 after the reaction?

<p>234 g (C)</p> Signup and view all the answers

What formula is used to calculate percent yield?

<p>Actual Yield / Theoretical Yield x 100 (C)</p> Signup and view all the answers

Which of the following statements about theoretical yield and actual yield is true?

<p>Theoretical yield is the maximum amount of product expected. (A)</p> Signup and view all the answers

In the reaction of manganese dioxide with hydrochloric acid, if 0.86 mol of MnO2 is used, how would you determine the excess reagent?

<p>Compare moles of MnO2 with HCl based on the balanced equation. (C)</p> Signup and view all the answers

When combining reactants, what step is crucial to find out which is the limiting reagent?

<p>Divide the number of moles of each reactant by the coefficients in the balanced equation. (B)</p> Signup and view all the answers

If 48.2 g of HCl reacts with 0.86 mol of MnO2, what reagent will likely be used up first?

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

Using the information provided, if 18.6 g of Cl2 is collected from the reaction, what does this represent?

<p>Actual yield (C)</p> Signup and view all the answers

In the balanced equation 2C2H6 + 7O2 → 4CO2 + 6H2O, how many atoms of oxygen are present on the reactants side?

<p>14 (C)</p> Signup and view all the answers

What is the molar mass of methanol (CH3OH) used in the combustion reaction?

<p>32.0 g (D)</p> Signup and view all the answers

What is the empirical formula of a compound with 0.108 mol of nitrogen and 0.217 mol of oxygen?

<p>NO2 (C)</p> Signup and view all the answers

Which reagent is described as the limiting reagent in the reaction 2NO + O2 → 2NO2?

<p>NO (D)</p> Signup and view all the answers

When balancing the equation C2H6 + O2 -> CO2 + H2O, which coefficient should be used for H2O in the balanced equation?

<p>3 (D)</p> Signup and view all the answers

What is the first step in calculating the quantity of a product in a chemical reaction?

<p>Write a balanced chemical equation (C)</p> Signup and view all the answers

In a chemical reaction, if 48.6 grams of magnesium reacts with 32.0 grams of oxygen to produce 80.6 grams of magnesium oxide, what is the mass change of the reactants?

<p>0 grams (C)</p> Signup and view all the answers

Which statement correctly describes the process of determining the molecular formula from the empirical formula NO2?

<p>The molecular formula is found by multiplying the empirical formula's subscripts by a whole number. (A)</p> Signup and view all the answers

How do you calculate the mass of water produced from 209 g of methanol in combustion?

<p>Convert grams of methanol to moles, then to moles of water, and back to grams (C)</p> Signup and view all the answers

If a certain reaction has an excess reagent, what does this imply about the other reactants?

<p>They are completely consumed (D)</p> Signup and view all the answers

In the reaction of ethane with oxygen, which order of balancing should be followed as indicated in the balancing procedure?

<p>Balance the element appearing in only one reactant and product first. (C)</p> Signup and view all the answers

Which term refers to the reactant that is not completely consumed in a chemical reaction?

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

In a balanced chemical equation, what do the stoichiometric coefficients indicate?

<p>The ratio of moles of each substance involved (B)</p> Signup and view all the answers

When balancing the equation C2H6 + O2 → CO2 + H2O, what is the next step after multiplying O2 by 7?

<p>Ensure the same number of each type of atom on both sides (D)</p> Signup and view all the answers

What is indicated by the total number of moles of reactants compared to the total number of moles of products in a balanced chemical equation?

<p>The law of conservation of mass is upheld. (A)</p> Signup and view all the answers

What must not be changed when balancing chemical equations?

<p>The subscripts (D)</p> Signup and view all the answers

In a reaction producing two products, if one product has a higher stoichiometric coefficient than the other, what can be inferred about the limiting reactant?

<p>It is completely consumed when the reaction goes to completion. (C)</p> Signup and view all the answers

What is the empirical molar mass of the compound NO2?

<p>46.01 g (A)</p> Signup and view all the answers

Flashcards

Stoichiometry

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

Stoichiometric Coefficients

The coefficients in a balanced chemical equation indicate the number of moles of each substance involved.

Balanced Chemical Equation

A balanced chemical equation ensures that the number of atoms of each element on the reactant side equals the number on the product side.

Limiting Reagent

The reactant that gets used up completely first in a chemical reaction, limiting the amount of product that can be formed.

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Excess Reagent

The reactant that is present in excess, meaning some of it will be left over after the reaction is complete.

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Mole Method

A set of steps used to calculate the amount of a reactant or product in a chemical reaction, starting from a known quantity of another substance.

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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 chemical equation.

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Molar Mass

The mass of a substance that contains one mole of that substance.

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Chemical Reaction

The process where substances change into new substances. For example, burning wood transforms wood into ash, smoke, and gases.

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Chemical Equation

Uses chemical symbols to show what happens during a chemical reaction. It represents the reactants on the left side and the products on the right side.

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Reactants

The substances that go into a chemical reaction, appearing on the left side of the equation.

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Products

The substances that are formed in a chemical reaction, appearing on the right side of the equation.

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Empirical Formula

The smallest whole-number ratio of atoms in a compound. It represents the simplest formula for a compound.

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Coefficients

Numbers in front of chemical formulas in a balanced equation. They represent the relative number of moles of each reactant and product.

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Formula Unit

The smallest unit of a compound, made up of atoms held together by chemical bonds.

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Molecular Formula Multiplier

The ratio of the molar mass of a compound to the molar mass of its empirical formula.

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What is the limiting reagent?

The reactant that is completely consumed first in a chemical reaction, limiting the amount of product that can be formed.

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What is the excess reagent?

The reactant present in excess, meaning some will be left over after the reaction is complete.

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What is theoretical yield?

The maximum amount of product that could be formed from a given amount of reactants, assuming 100% efficiency.

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What is actual yield?

The actual amount of product obtained from a chemical reaction.

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What is percent yield?

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

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What's the mole method?

A step-by-step method used to calculate the amount of a reactant or product in a chemical reaction, starting from a known quantity of another substance.

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How do you balance a chemical equation?

The process of adjusting the coefficients in a chemical equation to balance the number of atoms of each element on both sides.

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What is molar mass?

The mass of one mole of a substance.

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How do you determine the limiting reagent?

The process of determining the limiting reagent in a chemical reaction.

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What is mass?

The amount of a reactant or product in a chemical reaction, expressed in grams.

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What is a limiting reactant?

The reactant that is completely consumed first in a chemical reaction, thereby limiting the amount of product that can be formed.

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What is an excess reactant?

The reactant that is present in an amount greater than what is needed to react completely with the limiting reactant.

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How do you calculate the theoretical yield?

The amount of product that can be formed from a given amount of reactant.

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How do you identify the limiting reactant?

  1. Calculate the amount of product (moles or grams) that can be formed from each reactant.
  2. Determine which reactant is the limiting reactant by comparing the calculated product amounts. The reactant that produces the least amount of product is the limiting reactant.
  3. Use the limiting reactant to calculate the amount of product formed.
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How do you calculate the amount of excess reactant remaining?

  1. Calculate the amount of the excess reactant needed to react completely with the limiting reactant.
  2. Subtract this amount from the initial amount of the excess reactant to find the amount remaining.
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Study Notes

Mass Relationships in Chemical Reactions

  • This chapter explores the quantitative relationships between substances in chemical reactions.
  • It bridges the micro world (atoms and molecules) with the macro world (moles).
  • Atomic mass is the mass of an atom in atomic mass units (amu).
  • Mass number is equal to atomic mass in amu.

Atomic Mass or Atomic Weight

  • Atomic mass is the mass of an atom in atomic mass units (amu).
  • Example: 1H = 1.001 amu, 12C = 12.00 amu, 16O = 16.00 amu.
  • 1 amu is exactly 1/12 the mass of a 12C atom.

Average Atomic Mass

  • The average atomic mass, is a weighed average of all the isotopes present in a sample.
  • Isotopes have differing numbers of neutrons, but the same number of protons and electrons.
  • This average considers the natural abundance of each isotope.

Avogadro's Number

  • One mole (mol) of a substance contains Avogadro's number of elementary units.
  • Avogadro's number (Nₐ) is 6.022 x 10²³.
  • One mole of 12C atoms is exactly 12 grams.

Molar Mass

  • The molar mass is the mass of one mole of a substance, typically expressed in grams per mole (g/mol).
  • It is numerically equal to the atomic or molecular/formula mass in amu.

Molecular Mass

  • The molecular mass is the sum of the atomic masses (in amu) of all atoms in a molecule.
  • Example: SO₂ has a molecular mass of 64.07 amu (32.07 + 2 * 16.00).
  • Molecular mass (amu) = molar mass (grams).

Formula Mass

  • The formula mass is the sum of the atomic masses in a formula unit of an ionic compound.
  • Example: NaCl has a formula mass of 58.44 amu (22.99 + 35.45).
  • Formula mass (amu) = molar mass (grams).

Percent Composition of Compounds

  • This calculates the percentage of each element by mass within a compound.
  • Percent composition = (n x molar mass of element / molar mass of compound) x 100%
  • Where n is the number of moles of the element in one mole of the compound.

Determination of Empirical Formula

  • A method to determine the simplest whole-number ratio of atoms in a compound.
  • Steps involve converting percentages (if given) to masses, then mass to moles, then dividing by the smallest number of moles derived.

Determination of Molecular Formula

  • This formula describes the actual number of atoms of each element.
  • It's based on the empirical formula and the compound's molar mass.
  • x = molar mass / empirical molar mass

Limiting Reactants

  • A limiting reactant is a reactant that is completely consumed during a chemical reaction, limiting the amount of product that can be formed.
  • An excess reactant remains after the reaction; there's more of it than required.
  • Method one determines the amount of product formed from each reactant to pinpoint the limiting reagent.
  • Method two compares the mole ratios of reactants to locate the limiting reactant.

Reaction Yield

  • Theoretical yield is the maximum amount of product that can be produced.
  • Actual yield is the measured amount of product produced.
  • Percentage yield = (actual yield/ theoretical yield) x 100 %

Chemical Reactions and Equations

  • Chemical reactions involve a transformation of substances into other substances.
  • A chemical equation uses symbols to represent these transformations.
  • The equation's coefficients represent the mole ratios.

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Mass Relationships in Chemical Reactions PDF

Description

This quiz explores the concept of limiting reactants in chemical reactions, focusing on calculations involving excess reactants, theoretical yields, and percent yields. Test your understanding of these fundamental principles with practical examples and problem-solving scenarios.

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